| | \documentclass[a4paper]{article} |
|---|
| | |
|---|
| | \usepackage{natbib} |
|---|
| | \usepackage[dvips,margin=3cm]{geometry} |
|---|
| | \usepackage{graphicx} |
|---|
| | \usepackage{amssymb} |
|---|
| | \usepackage{units} |
|---|
| | \usepackage{url} |
|---|
| | \usepackage{flafter} |
|---|
| | |
|---|
| | \title{\textbf{Assessing the efficacy of a touch screen overlay as a selection |
|---|
| | device for typical GUI targets}} |
|---|
| | \author{M.\ GLEESON\dag, N.\ STANGER\thanks{Corresponding author. Email nstanger@infoscience.otago.ac.nz.} \dag\ and E.\ FERGUSON\ddag} |
|---|
| | \date{\dag Department of Information Science, \\ |
|---|
| | \ddag Department of Human Nutrition, \\ |
|---|
| | University of Otago, Dunedin, New Zealand} |
|---|
| | |
|---|
| | |
|---|
| | \begin{document} |
|---|
| | |
|---|
| | \renewcommand{\baselinestretch}{2} |
|---|
| | |
|---|
| | \maketitle |
|---|
| | |
|---|
| | \begin{quotation} |
|---|
| | \noindent In this paper we investigate the efficacy of a touch |
|---|
| | screen overlay compared to a mouse, when selecting typical graphical |
|---|
| | user interface (GUI) items in a desktop information system. A series |
|---|
| | of tests were completed involving multi-directional point and select |
|---|
| | tasks, and the results for both devices compared. The results showed |
|---|
| | that the touch screen overlay was not suitable for selecting GUI |
|---|
| | targets smaller than \unit[4]{mm}. The touch screen overlay was |
|---|
| | slower and had a higher error rate than the mouse, but there was no |
|---|
| | significant difference in throughput. Testers rated the mouse easier |
|---|
| | to use and to make accurate selections, while the touch screen |
|---|
| | overlay resulted in greater arm, wrist and finger fatigue. These |
|---|
| | results suggest that a touch screen overlay is not a practical |
|---|
| | selection device for desktop interfaces with small GUI targets. |
|---|
| | \end{quotation} |
|---|
| | |
|---|
| | \begin{quotation} |
|---|
| | \noindent \emph{Keywords:} Touch screen overlay; Mouse; Selection |
|---|
| | device; Fitts' Law; Performance evaluation; GUI item |
|---|
| | \end{quotation} |
|---|
| | |
|---|
| | % main text |
|---|
| | \newcommand{\ISOnine}{ISO 9241-9} |
|---|
| | |
|---|
| | |
|---|
| | \section{Introduction} |
|---|
| | \label{sec-introduction} |
|---|
| | |
|---|
| | Most modern information systems that run on desktop personal computers |
|---|
| | are designed to be used with a keyboard and mouse. While the combination |
|---|
| | of keyboard and mouse is the accepted method of interaction with such |
|---|
| | systems it does not necessarily suit all information systems. |
|---|
| | Information systems with limited data entry may be more usable through |
|---|
| | the use of a keyboard and touch screen. Touch screens require less |
|---|
| | physical space and thus the workstation environment in an office setting |
|---|
| | could be improved, allocating more space to the user and less to the |
|---|
| | computer. |
|---|
| | |
|---|
| | The purpose of this paper is to investigate how effective a touch screen |
|---|
| | overlay is compared to a mouse, when selecting typical graphical user |
|---|
| | interface (GUI) items. The target types tested were buttons, check |
|---|
| | boxes, combo boxes and text boxes, which are typical of those found in |
|---|
| | an interface for an information system. Each target type was tested at |
|---|
| | three different sizes (see Section~\ref{sec-GUI}). |
|---|
| | |
|---|
| | A typical touch screen device comprises a monitor enhanced with hardware |
|---|
| | for detecting touches on the screen surface. An alternative approach is |
|---|
| | to attach a discrete touch-sensitive surface to an existing conventional |
|---|
| | monitor. \citet{Sear-A-1991-IJMMS} have previously assessed the efficacy |
|---|
| | of specialised touch screen hardware, but there appears to have been |
|---|
| | little research into the efficacy of touch screen overlays. We therefore |
|---|
| | chose to compare the performance of a touch screen overlay with that of |
|---|
| | a mouse. |
|---|
| | |
|---|
| | The testing occurred in the context of a research project undertaken by |
|---|
| | the Department of Human Nutrition at the University of Otago. This |
|---|
| | project aims to improve complementary feeding diets for toddlers in New |
|---|
| | Zealand, by designing a computer program to help formulate |
|---|
| | population-specific food-based dietary guidelines for this high risk |
|---|
| | group. The program, which is based on a previously published linear |
|---|
| | programming approach \citep{Ferg-EL-2004-Nutrition}, is a |
|---|
| | decision-making tool, designed specifically for nutrition programme |
|---|
| | planners to assist them in selecting appropriate and improved home-based |
|---|
| | complementary foods. |
|---|
| | |
|---|
| | % do we need this? |
|---|
| | The remainder of the paper discusses our experiment and the results |
|---|
| | obtained. Section~\ref{sec-GUI} briefly describes the types of targets |
|---|
| | used in the experiment, while Section~\ref{sec-evaluation} describes the |
|---|
| | measures used to evaluate the selection devices. The experimental design |
|---|
| | is described in Section~\ref{sec-method}. Section~\ref{sec-analysis} |
|---|
| | describes how the data were analysed, and Section~\ref{sec-results} |
|---|
| | presents the results of the experiment. Our conclusions are presented in |
|---|
| | Section~\ref{sec-conclusions}. |
|---|
| | |
|---|
| | |
|---|
| | \section{GUI targets} |
|---|
| | \label{sec-GUI} |
|---|
| | |
|---|
| | Since the 1980's much work has gone into developing human computer |
|---|
| | interface guidelines. Today's interfaces are made up of a combination of |
|---|
| | different targets that include text boxes, check boxes, combo boxes, |
|---|
| | list boxes, buttons, labels, tool bars, etc. \citet{Sear-A-1991-IJMMS} |
|---|
| | showed that touch screens can be successfully used as a selection device |
|---|
| | and can have advantages over a mouse, even for small targets. These |
|---|
| | results were, however, based on selecting arbitrary shapes and not the |
|---|
| | typical targets found in modern GUIs. |
|---|
| | |
|---|
| | To accurately test the performance of each selection device within the |
|---|
| | experiment, three different sizes of GUI target were used, corresponding |
|---|
| | to small, medium and large GUI items. As our experiment took place in a |
|---|
| | Windows environment, we would have preferred to base these sizes on |
|---|
| | Microsoft's user interface guidelines. However, Microsoft's guidelines |
|---|
| | specify only a single standard size for most GUI items \citep[pp.\ |
|---|
| | 448--450]{MS-1999-UI}. \citeauthor{Appl-2004-HIG}'s |
|---|
| | \citeyearpar{Appl-2004-HIG} human interface guidelines specify three |
|---|
| | standard sizes (mini, small and large), but these proved to be rather |
|---|
| | small in our Windows-based testing environment. We therefore adjusted |
|---|
| | Apple's three sizes such that the ``small'' size was consistent with |
|---|
| | Microsoft's guidelines. The resultant target sizes are listed in |
|---|
| | Table~\ref{tab-target-sizes}. A screen resolution of \unit[81]{DPI} was |
|---|
| | assumed. |
|---|
| | |
|---|
| | |
|---|
| | \begin{table}[ht] |
|---|
| | \caption{Target sizes (width \(\times\) height) used in the experiment.} |
|---|
| | \label{tab-target-sizes} |
|---|
| | \begin{tabular}{llll} |
|---|
| | \hline |
|---|
| | \textbf{Target type} & \textbf{Large} & \textbf{Medium} & \textbf{Small} \\ |
|---|
| | \hline |
|---|
| | Text box & \(\unit[63]{mm} \times \unit[11]{mm}\) & \(\unit[55]{mm} \times \unit[8]{mm}\) & \(\unit[47]{mm} \times \unit[6]{mm}\) \\ |
|---|
| | Combo box & \(\unit[63]{mm} \times \unit[11]{mm}\) & \(\unit[55]{mm} \times \unit[8]{mm}\) & \(\unit[47]{mm} \times \unit[6]{mm}\) \\ |
|---|
| | Button & \(\unit[28]{mm} \times \unit[13]{mm}\) & \(\unit[24]{mm} \times \unit[9]{mm}\) & \(\unit[17]{mm} \times \unit[6]{mm}\) \\ |
|---|
| | Check box\(^{a}\) & \(\unit[9]{mm} \times \unit[9]{mm}\) & \(\unit[6]{mm} \times \unit[6]{mm}\) & \(\unit[4]{mm} \times \unit[4]{mm}\) \\ |
|---|
| | \hline |
|---|
| | \end{tabular} |
|---|
| | |
|---|
| | {\footnotesize \(^{a}\)This refers to the size of the check box itself, not the associated text label.} |
|---|
| | \end{table} |
|---|
| | |
|---|
| | |
|---|
| | \section{Evaluation methods} |
|---|
| | \label{sec-evaluation} |
|---|
| | |
|---|
| | Each selection device was assessed using a combination of performance |
|---|
| | and comfort measures. The performance measures were primarily taken from |
|---|
| | the \ISOnine\ standard \citep{ISO-2000-9241-9}, while the comfort |
|---|
| | measures were derived from a questionnaire administered to test |
|---|
| | participants. |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Performance} |
|---|
| | \label{sec-evaluation-performance} |
|---|
| | |
|---|
| | ISO 9241 specifies standards for the ergonomic design of office |
|---|
| | computing environments. Part 9 of this standard describes different |
|---|
| | tests that can be used to evaluate one or more pointing devices |
|---|
| | \citep{ISO-2000-9241-9}. The standard describes a serial point and |
|---|
| | select task and recognises a dependent measure used with this test, |
|---|
| | known as \emph{throughput}. The serial test comprises moving the cursor |
|---|
| | back and forth between two targets using the pointing device and |
|---|
| | selecting each target by pressing and releasing a button on the pointing |
|---|
| | device. One disadvantage of this approach is that only two targets are |
|---|
| | used in the test and therefore interactions between more than two |
|---|
| | targets---which often occur in a typical information system |
|---|
| | interface---are not studied. |
|---|
| | |
|---|
| | \citet{Mack-IS-2001-EHCI} note that throughput is a very important |
|---|
| | measure, as it reflects the efficiency of the user completing the task |
|---|
| | and is a measure of both speed and accuracy. Throughput is calculated by |
|---|
| | the formula \(\mathit{throughput} = \mathit{ID}_{e} / \mathit{MT}\), |
|---|
| | where \(\mathit{MT}\) is the movement time in seconds (defined as the |
|---|
| | time taken to successfully select a target) and \(\mathit{ID}_{e}\) is |
|---|
| | Fitts' \citeyearpar{Fitt-PM-1954-Law} \emph{index of difficulty} |
|---|
| | measured in bits. Throughput is thus measured in bits per second (bps). |
|---|
| | |
|---|
| | The index of difficulty is calculated by the formula \(\mathit{ID}_{e} = |
|---|
| | \log_{2}((D / W_{e}) + 1)\), where \(D\) is the distance to the target |
|---|
| | and \(W_{e}\) is the \emph{effective width} of the target. The effective |
|---|
| | width reflects spatial variability in a sequence of trials, and thus |
|---|
| | differs from the actual width of the target. The effective width of a |
|---|
| | target is calculated by the formula \(W_{e} = 4.133 \times |
|---|
| | \mathit{SD}_{x}\), where \(\mathit{SD}_{x}\) is the standard deviation |
|---|
| | in the selection coordinates measured along the path to target \(x\). |
|---|
| | |
|---|
| | \ISOnine\ does not provide any guidance on the range of index of |
|---|
| | difficulty values to use in testing. \citet{Doug-SA-1999-CHI} recommend |
|---|
| | using a range from 2 to 6 bits. They also recommend calculating the |
|---|
| | \emph{error rate} as a separate dependent measure of accuracy. The |
|---|
| | error rate is defined as the ratio of incorrect to correct selections |
|---|
| | made on a target, so an error rate of 100\% implies that there were as |
|---|
| | many errors made as correct selections. Error rate is not included in |
|---|
| | \ISOnine, but has been used in several other studies |
|---|
| | \citep{Sear-A-1991-IJMMS,Sear-A-1993-BIT,Hara-H-1996,Bend-G-1999-PhD, |
|---|
| | Doug-SA-1999-CHI,Mack-IS-2001-EHCI,Po-BA-2004-CHI}. Computing both |
|---|
| | throughput and error rate gives a more detailed performance analysis for |
|---|
| | the selection device in question. |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Comfort} |
|---|
| | \label{sec-evaluation-comfort} |
|---|
| | |
|---|
| | ISO 9241-9 argues that to fully evaluate a selection device requires |
|---|
| | assessment of user effort and comfort in addition to performance |
|---|
| | measurements. Comfort is subjective and can be assessed by means of |
|---|
| | questionnaires, while effort can be evaluated objectively by measuring |
|---|
| | the biomechanical load on users as they use a device. Unfortunately, |
|---|
| | such measurements require reasonably sophisticated equipment |
|---|
| | \citep{Doug-SA-1999-CHI} that was not available to us. We therefore |
|---|
| | omitted effort measurements from our experiment. |
|---|
| | |
|---|
| | A questionnaire was used to assess comfort and user satisfaction for |
|---|
| | each selection device in our experiment. The selection device assessment |
|---|
| | questionnaire comprised sixteen questions, eight of which were taken |
|---|
| | from the ISO ``Independent Questionnaire for Assessment of Comfort'' |
|---|
| | \citep{Doug-SA-1999-CHI}. The remaining eight questions related |
|---|
| | specifically to the target types and target sizes that were tested. In |
|---|
| | particular, the questionnaire aimed to assess the participants' comfort |
|---|
| | in using the selection device, the difficulty in accurately selecting each |
|---|
| | of the target types and the preferred size of each target type using the |
|---|
| | selection device. |
|---|
| | |
|---|
| | The responses to twelve of the questions were based on a five point |
|---|
| | ordinal scale. The remaining four questions referred to the |
|---|
| | participant's preferred size for each target type and were based on a |
|---|
| | three point response corresponding to the target sizes tested---small, |
|---|
| | medium and large (see Table~\ref{tab-target-sizes}). There was also a |
|---|
| | space for participants to provide additional general feedback about the |
|---|
| | testing process. |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Other considerations} |
|---|
| | \label{sec-evaluation-other} |
|---|
| | |
|---|
| | \citet{Doug-SA-1999-CHI} also note that \ISOnine\ does not take into |
|---|
| | account any possible effects of learning, which can affect movement time |
|---|
| | and accuracy. For example, \citet{Mack-IS-1991} found that the movement |
|---|
| | times from the first of five testing sessions were significantly higher |
|---|
| | than in later sessions. This can be explained as a result of learning |
|---|
| | and shows that input device studies should take learning into account |
|---|
| | and test for it; indeed, \citet{Doug-SA-1999-CHI} recommend applying a |
|---|
| | repeated measures paradigm and testing for learning effects. |
|---|
| | |
|---|
| | One interesting aspect of using typical GUI items as targets is the |
|---|
| | variation in selection behaviour for different target types, compared to |
|---|
| | earlier studies that used simple rectangular targets. The button, check |
|---|
| | box and text box target types can be said to exhibit a ``one-step'' |
|---|
| | selection behaviour, because they require only single action (i.e., the |
|---|
| | user clicks on them) in order to be selected. A combo box is different, |
|---|
| | however, because it exhibits a ``two-step'' selection behaviour: first |
|---|
| | the combo box must be selected in order to show the list of items, and |
|---|
| | then an item must be selected from the displayed list, as illustrated in |
|---|
| | Figure~\ref{fig-combo-box}. To complicate matters further, users may |
|---|
| | execute this two-step behaviour using either a ``one-click'' or a |
|---|
| | ``two-click'' approach. In the former approach, the user clicks on the |
|---|
| | combo box, drags down to the desired list item, then releases. In the |
|---|
| | latter approach, the user clicks once on the combo box, then clicks |
|---|
| | again on the desired list item. If the drop-down list were longer than |
|---|
| | what could be displayed on screen, this could even lead to a |
|---|
| | ``multiple-click'' approach, where the user clicks multiple times on the |
|---|
| | downward scroll arrow in the list. We have, however, not considered this |
|---|
| | possibility in our experiment. |
|---|
| | |
|---|
| | |
|---|
| | \begin{figure}[ht] |
|---|
| | \centering |
|---|
| | \includegraphics[scale=0.8]{combobox-step1}\quad\quad\quad |
|---|
| | \includegraphics[scale=0.8]{combobox-step2} |
|---|
| | \caption{The ``two-step'' action required to select a combo box.} |
|---|
| | \label{fig-combo-box} |
|---|
| | \end{figure} |
|---|
| | |
|---|
| | |
|---|
| | |
|---|
| | \section{Method} |
|---|
| | \label{sec-method} |
|---|
| | |
|---|
| | An experiment was carried out to test the effect of size for different |
|---|
| | GUI target types with different selection devices. The experiment |
|---|
| | involved participants completing a series of simple point and select |
|---|
| | tasks. Small, medium and large sizes (see Table~\ref{tab-target-sizes}) |
|---|
| | were tested for combo boxes, text boxes, check boxes and buttons, using |
|---|
| | either a touch screen overlay or a mouse. The test was |
|---|
| | multi-directional, meaning the targets appeared in multiple directions |
|---|
| | from the initial starting point. A variety of different sizes, angles |
|---|
| | and distances were used for each target position. |
|---|
| | |
|---|
| | The test itself comprised a screen containing a button in the centre and |
|---|
| | a target for the participant to select as illustrated in |
|---|
| | Figure~\ref{fig-test-environment}. When a participant clicked on the |
|---|
| | centre ``Go'' button, a trial was started and a target appeared on the |
|---|
| | screen. The trial ended when the participant successfully clicked the |
|---|
| | target, which then disappeared. The time taken between clicking the |
|---|
| | ``Go'' button and successfully clicking on the target was recorded as |
|---|
| | well as the number of errors made during the trial. The final |
|---|
| | coordinates of the successful click on the target were recorded in order |
|---|
| | to calculate the effective width of the target. |
|---|
| | |
|---|
| | |
|---|
| | \begin{figure} |
|---|
| | \centering |
|---|
| | \includegraphics[scale=0.5]{test-environment} |
|---|
| | \caption{Screenshot of the test environment with a target in the |
|---|
| | top left of the screen and the ``Go'' button in the centre.} |
|---|
| | \label{fig-test-environment} |
|---|
| | \end{figure} |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Participants} |
|---|
| | \label{sec-method-participants} |
|---|
| | |
|---|
| | A participant sample size of twenty-four was used for the experiment. |
|---|
| | Each participant was allocated to one of two groups with each group |
|---|
| | using one selection device in testing. The allocation of groups was |
|---|
| | based on the results of a questionnaire completed by each participant |
|---|
| | prior to testing. The purpose of the pre-test questionnaire was to |
|---|
| | establish the level of computer, mouse and touch screen experience of |
|---|
| | each participant. Participants were then allocated to a selection device |
|---|
| | group based on which device they had the least experience with. |
|---|
| | |
|---|
| | Due to the testing being done within the nutrition program environment |
|---|
| | mentioned in Section~\ref{sec-introduction}, the participants were all |
|---|
| | nutritionists (i.e., typical users of the program). There were |
|---|
| | twenty-one female and three male participants, all with a university |
|---|
| | level of education. All participants were unpaid volunteers. |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Apparatus} |
|---|
| | \label{sec-method-apparatus} |
|---|
| | |
|---|
| | The test environment was implemented in Visual Basic.NET using Microsoft |
|---|
| | Studio 2003, and is illustrated in Figure~\ref{fig-test-environment}. |
|---|
| | During each test, data corresponding to the relevant measures (movement |
|---|
| | time, number of errors and selection coordinates) were captured by the |
|---|
| | software and automatically written to a Microsoft Excel worksheet. |
|---|
| | |
|---|
| | The touch screen used in testing was a 17'' Magic Touch USB overlay |
|---|
| | Model KTMT-1700-USB-M \citep{Keyt-2005-Touch}. This device uses a |
|---|
| | take-off touch strategy, that is, a selection is not confirmed until the |
|---|
| | user's finger is removed from the screen. An important property of touch |
|---|
| | screen overlays is that they are placed over a conventional monitor and |
|---|
| | the touch surface is thus not coincident with the display surface. This |
|---|
| | can cause a slight discrepancy or parallax effect between where the user |
|---|
| | touches the overlay and where the cursor is positioned on the screen. |
|---|
| | |
|---|
| | The touch screen overlay was fitted to a Dell 15'' Flat Panel Model |
|---|
| | E151FPb monitor. A flat panel monitor was chosen because it was noticed |
|---|
| | during pre-testing that typical CRT monitors with curved screens |
|---|
| | produced a variable gap between the overlay and the display surface, |
|---|
| | thus potentially leading to a greater parallax effect than with a flat |
|---|
| | display surface. |
|---|
| | |
|---|
| | The mouse used in testing was a standard Dell PS/2 Optical Mouse Model |
|---|
| | M071KC. Both devices were connected to a Dell Inspiron 7500 laptop |
|---|
| | computer that ran the testing software. |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Design} |
|---|
| | \label{sec-method-design} |
|---|
| | |
|---|
| | A mixed design experiment was used with the selection device as a |
|---|
| | between-subjects factor. The independent (between-subject) variables |
|---|
| | were: |
|---|
| | \begin{itemize} |
|---|
| | |
|---|
| | \item Target type (text box, combo box, button and check box) |
|---|
| | |
|---|
| | \item Target size (large, medium and small---see |
|---|
| | Table~\ref{tab-target-sizes}) |
|---|
| | |
|---|
| | \item Target distance (\unit[40]{mm}, \unit[80]{mm} and |
|---|
| | \unit[160]{mm}---see below) |
|---|
| | |
|---|
| | \item Target angle (\(45^{\circ}\), \(135^{\circ}\), \(225^{\circ}\) |
|---|
| | and \(315^{\circ}\)---see below) |
|---|
| | |
|---|
| | \item Trial (1 to 144) |
|---|
| | |
|---|
| | \item Block (1 to 6) |
|---|
| | |
|---|
| | \end{itemize} |
|---|
| | The dependent variables within the experiment were throughput, movement |
|---|
| | time and error rate. |
|---|
| | |
|---|
| | The entire test was divided into six blocks. Each block contained every |
|---|
| | possible combination of target type (four combinations), size (three |
|---|
| | combinations), angle from initial starting point (four combinations) and |
|---|
| | distance from initial starting point (three combinations). Consequently |
|---|
| | there were 144 trials in each block and the entire experiment per |
|---|
| | participant comprised a total of 864 trials (six blocks of 144 trials |
|---|
| | each). Combinations of target type, distance and angle were presented to |
|---|
| | the participant in random sequence with no repetition. Target size was |
|---|
| | deliberately set to large for the first forty-eight trials in each block, |
|---|
| | followed by medium for the next forty-eight trials, and finally small for |
|---|
| | the remaining trials, in order to compensate for learning effects. |
|---|
| | |
|---|
| | The combination of distance and angle from the initial starting point |
|---|
| | yielded twelve possible target positions for each trial, as illustrated |
|---|
| | in Figure~\ref{fig-target-positions}. Three distances were used that |
|---|
| | represented target positions ranging from close to the initial starting |
|---|
| | point to very far away from the initial starting point. Four angles were |
|---|
| | chosen so that targets could be tested in ninety degree blocks and to |
|---|
| | provide a good range of screen positions for the target. The first angle |
|---|
| | was set to \(45^{\circ}\) with \(90^{\circ}\) increments thereafter, in |
|---|
| | order to mimic real life user interface target selection, where targets |
|---|
| | are situated in different areas of the screen and therefore selections |
|---|
| | are made in multiple directions that are neither simply horizontal nor |
|---|
| | vertical. |
|---|
| | |
|---|
| | |
|---|
| | \begin{figure} |
|---|
| | \centering |
|---|
| | \includegraphics{target-positions} |
|---|
| | \caption{Positions of targets tested. The black box represents the |
|---|
| | initial starting point and the rounded rectangles represent the |
|---|
| | target positions.} |
|---|
| | \label{fig-target-positions} |
|---|
| | \end{figure} |
|---|
| | |
|---|
| | |
|---|
| | The index of difficulty (\(\mathit{ID}_{e}\)) was ascertained for each |
|---|
| | possible task using the combination of distance and non-adjusted target |
|---|
| | width. This showed that the test had a range of \(\mathit{ID}_{e}\) |
|---|
| | values from \unit[0.7]{bits} (\unit[63]{mm} width and \unit[160]{mm} |
|---|
| | distance) to \unit[5.4]{bits} (\unit[4]{mm} width and \unit[40]{mm} |
|---|
| | distance). It is important to note that the combo box distance values |
|---|
| | were adjusted in these calculations to reflect the two-step selection |
|---|
| | behaviour of this target type (as discussed in |
|---|
| | Section~\ref{sec-evaluation-other}). That is, we need to consider not |
|---|
| | just the distance from the initial starting point to the target, but |
|---|
| | also the extra distance from the main combo box to the selected list |
|---|
| | item. In our experiment, participants were told to always select the |
|---|
| | third list item in combo boxes (as illustrated in |
|---|
| | Figure~\ref{fig-combo-box}), so the adjusted distance for a combo box |
|---|
| | was equal to the normal distance from the initial starting point to the |
|---|
| | target, \emph{plus} the additional distance to the third list item. |
|---|
| | Additional data about the selections made on combo boxes were recorded |
|---|
| | in order to account for the selection approach of the participant, |
|---|
| | whether it be a ``one-click'' or ``two-click'' approach. |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Procedure} |
|---|
| | \label{sec-method-procedure} |
|---|
| | |
|---|
| | The participant was given an introduction to the test by the research |
|---|
| | observer, which included a brief summary of the aims of the study and |
|---|
| | what the test involved. The participant was also given an instruction |
|---|
| | sheet that they had access to throughout the duration of the test. After |
|---|
| | reading the instruction sheet the participant had the opportunity to ask |
|---|
| | questions or raise any issues. |
|---|
| | |
|---|
| | Participants were instructed to complete each block of trials as quickly |
|---|
| | as possible without losing accuracy. Participants were given the |
|---|
| | opportunity to rest for as long as they wished between blocks. It was |
|---|
| | made clear to participants that a task was only complete once the target |
|---|
| | was successfully selected. |
|---|
| | |
|---|
| | Before the test began, participants were instructed to complete a |
|---|
| | practice session involving fifteen random trials of the same point and |
|---|
| | select tasks used in the test. This brought all participants up to a |
|---|
| | minimal level of experience with their selection device. This also meant |
|---|
| | that each participant knew how to correctly select each target type |
|---|
| | including the combo box. |
|---|
| | |
|---|
| | At the conclusion of the test the participant was asked to fill out a |
|---|
| | questionnaire regarding comfort and user satisfaction with the selection |
|---|
| | device used. |
|---|
| | |
|---|
| | |
|---|
| | \section{Analysis} |
|---|
| | \label{sec-analysis} |
|---|
| | |
|---|
| | The data collected from the software included movement time, error rate |
|---|
| | and throughput and was used to evaluate selection device performance. A |
|---|
| | mixed design repeated measures analysis of variance model (MANOVA) was |
|---|
| | used for movement time and throughput to examine within subject |
|---|
| | differences in target type and size, as well as between subject |
|---|
| | differences in selection device. A Greenhouse and Geisser correction of |
|---|
| | the F-ratio was used whenever the Mauchly's test results showed that |
|---|
| | assumptions of sphericity were violated. |
|---|
| | |
|---|
| | Post hoc tests, for multiple comparisons, were made using the Bonferroni |
|---|
| | method. Due to the skew observed in the error rate data (see |
|---|
| | Section~\ref{sec-results-learning}), inter-device differences in error |
|---|
| | rates were assessed using the Mann-Whitney U Test. |
|---|
| | |
|---|
| | The comfort questionnaire was based on a five point ordinal scale, where |
|---|
| | five generally indicated a poor rating. Because of the small data size, a |
|---|
| | Mann-Whitney (non-parametric) test was used. |
|---|
| | |
|---|
| | All statistical analyses were performed using SPSS version 11.0. A |
|---|
| | \emph{p}-value of \(< 0.05\) was considered statistically significant. |
|---|
| | |
|---|
| | |
|---|
| | \section{Results and discussion} |
|---|
| | \label{sec-results} |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Adjusting for learning} |
|---|
| | \label{sec-results-learning} |
|---|
| | |
|---|
| | \citet{Doug-SA-1999-CHI} have shown that the effects of learning can |
|---|
| | affect movement time and accuracy. They therefore recommend that input |
|---|
| | device studies should apply a repeated measures paradigm and test for |
|---|
| | learning effects. |
|---|
| | |
|---|
| | From analysing the results of movement time and throughput over each |
|---|
| | test block, it was clear for the combo box and check box target types |
|---|
| | that learning occurred from the first to the second block with the touch |
|---|
| | screen overlay, as seen in Figure~\ref{fig-movement-time-learning}. Due |
|---|
| | to prior participant experience, no learning was observed with the |
|---|
| | mouse. No learning occurred with the text box or button, most likely due |
|---|
| | to their relatively large size and simple selection behaviour. |
|---|
| | |
|---|
| | |
|---|
| | \begin{figure} |
|---|
| | \centering |
|---|
| | \includegraphics{combobox-learning} |
|---|
| | \includegraphics{checkbox-learning} |
|---|
| | \caption{Learning is displayed for movement time by selection device |
|---|
| | and test block for the combo box and check box.} |
|---|
| | \label{fig-movement-time-learning} |
|---|
| | \end{figure} |
|---|
| | |
|---|
| | |
|---|
| | Statistical analysis using a simple repeated measure ANOVA was carried |
|---|
| | out on movement time for both the check box and combo box. For movement |
|---|
| | time of the combo box, the effect of block \(\times\) device was |
|---|
| | significant \((F(1.549, 1335.219) = 4.373, p < 0.05)\). Helmhert |
|---|
| | contrasts showed that the differences between blocks became |
|---|
| | non-significant after block 1 \((p > 0.05)\), which implies that |
|---|
| | learning occurred during block 1. |
|---|
| | |
|---|
| | For movement time of the check box, the effect of block \(\times\) |
|---|
| | device was significant \((F(1.608, 1385.960) = 4.763, p < 0.05)\). |
|---|
| | Helmhert contrasts again showed that the differences between blocks |
|---|
| | became non-significant after block 1 \((p > 0.05)\), implying that |
|---|
| | learning occurred during block 1. |
|---|
| | |
|---|
| | To account for learning with the combo and check box, results from block |
|---|
| | 6 only were used to calculate the movement time and throughput measures, |
|---|
| | as the results from block 6 alone gave a good measure of performance. |
|---|
| | However, the error rate results were highly skewed for both target |
|---|
| | types, with two participants accounting for almost 90\% of the errors. |
|---|
| | Error rates for the check box and combo box were therefore calculated |
|---|
| | using results from all six test blocks. |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Movement time} |
|---|
| | \label{sec-results-movement} |
|---|
| | |
|---|
| | The results showed that the mouse had an overall movement time of |
|---|
| | \unit[1.32]{s} across all target types compared to \unit[1.57]{s} for |
|---|
| | the touch screen overlay. We can thus conclude that the touch screen |
|---|
| | overlay was on average 1.2 times slower than the mouse. This is |
|---|
| | interesting because \citet{Sear-A-1991-IJMMS} found that the movement |
|---|
| | times for mouse and touch screen monitor were similar for rectangular |
|---|
| | targets larger than \unit[2]{mm}. Therefore the nature of the two types |
|---|
| | of touch screen (overlay versus monitor) may affect the movement time |
|---|
| | associated with the type of touch screen. It is also likely that due to |
|---|
| | the loss of accuracy found with the overlay during testing, the touch |
|---|
| | screen monitor will have faster movement times compared to the touch |
|---|
| | screen overlay. |
|---|
| | |
|---|
| | The movement times for each target type showed that the text box had the |
|---|
| | fastest movement time, followed by the button, the check box and the |
|---|
| | combo box. These results are illustrated in |
|---|
| | Figure~\ref{fig-movement-time} and are consistent with Fitts' Law |
|---|
| | \citep{Fitt-PM-1954-Law}, in that the largest target (the text box) had |
|---|
| | the fastest movement time. It may appear that the combo box results |
|---|
| | violate Fitts' Law, as the combo box is the same size as the text box, |
|---|
| | yet is over twice as slow. In this case however, the slow movement times |
|---|
| | are not a function of the target size, but rather a result of the more |
|---|
| | complex two-step behaviour required to successfully select a combo box |
|---|
| | (which is not considered by Fitts' Law). The extra movement of selecting |
|---|
| | an item from the drop-down list clearly dramatically increases the |
|---|
| | movement time for the combo box. As the additional distance from the |
|---|
| | main combo box area to the list item is relatively short, the |
|---|
| | significant increase in movement time is therefore most likely due to |
|---|
| | users making more errors. |
|---|
| | |
|---|
| | |
|---|
| | \begin{figure} |
|---|
| | \centering |
|---|
| | \includegraphics{movement-time} |
|---|
| | \caption{Movement time by target type and device, averaged across |
|---|
| | all target sizes.} |
|---|
| | \label{fig-movement-time} |
|---|
| | \end{figure} |
|---|
| | |
|---|
| | |
|---|
| | The touch screen overlay was found to have similar movement time to the |
|---|
| | mouse for the medium and large targets, but for the small targets, the |
|---|
| | touch screen overlay was on average 1.5 times slower than the mouse. The |
|---|
| | only time that the touch screen overlay was found to be faster than the |
|---|
| | mouse was with the largest target type (the large text box), but the |
|---|
| | difference was less than one percent. |
|---|
| | |
|---|
| | The movement time for the small check box on the touch screen overlay |
|---|
| | was about 2.7 times slower than that for the mouse. The small check box |
|---|
| | was the smallest item tested, with dimensions of \unit[4]{mm} \(\times\) |
|---|
| | \unit[4]{mm}. We can conclude that the touch screen overlay was not |
|---|
| | efficient for selecting targets as small as \unit[4]{mm}. Compare this |
|---|
| | with \citet{Sear-A-1991-IJMMS}, who showed that a touch screen monitor |
|---|
| | has similar movement time to a mouse for targets as small as |
|---|
| | \unit[2]{mm}. While a touch screen monitor can be used with targets as |
|---|
| | small as \unit[2]{mm}, a touch screen overlay should only be used for |
|---|
| | targets with a size of greater than \unit[4]{mm}. The results from the |
|---|
| | error rate analysis also support this conclusion (see |
|---|
| | Section~\ref{sec-results-error-rate}). |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Throughput} |
|---|
| | \label{sec-results-throughput} |
|---|
| | |
|---|
| | The average throughput for the mouse was \unit[1.242]{bps}, slightly |
|---|
| | higher than the \unit[1.214]{bps} average throughput for the touch |
|---|
| | screen overlay. The selection device by itself was shown not to have a |
|---|
| | significant effect on throughput \((F(1, 22) = 0.02, p > 0.05)\). |
|---|
| | Throughput did not vary for size but throughput did vary depending on |
|---|
| | target type \((F(2.07, 45.55) = 4.77, p < 0.001)\), as shown in |
|---|
| | Figure~\ref{fig-throughput}. Check boxes had the highest throughput rate |
|---|
| | of \unit[1.967]{bps} (sd = 0.720). This is interesting as the check box |
|---|
| | had the second worst movement time and the worst error rate. Upon |
|---|
| | further investigation it was seen that the movement time for the check |
|---|
| | box was in fact in the middle range of all targets, and due to its small |
|---|
| | size it had a high index of difficulty. These two factors are the most |
|---|
| | likely reason for the check box having such a high throughput rate. |
|---|
| | |
|---|
| | |
|---|
| | \begin{figure}[ht] |
|---|
| | \centering |
|---|
| | \includegraphics{throughput} |
|---|
| | \caption{Throughput by target type and device, averaged across all |
|---|
| | target sizes.} |
|---|
| | \label{fig-throughput} |
|---|
| | \end{figure} |
|---|
| | |
|---|
| | |
|---|
| | The combo box had the worst average throughput of \unit[0.501]{bps} (sd |
|---|
| | = 0.213). The index of difficulty was not very high for the combo box, |
|---|
| | so its low throughput rate could be attributed to its high movement |
|---|
| | time. |
|---|
| | |
|---|
| | The average throughput rate of \unit[1.242]{bps} for the mouse is much |
|---|
| | lower than that found by previous research. A study by |
|---|
| | \citet{Doug-SA-1994-SIGCHI} showed that a mouse had a throughput rate of |
|---|
| | \unit[4.15]{bps}. \citet{Mack-IS-1991} compared three devices (mouse, |
|---|
| | tablet and trackball) using four target sizes (8, 16, 32 and 64 pixels) |
|---|
| | over two different types of tasks (pointing and dragging), and found |
|---|
| | that the throughput for the mouse was \unit[4.5]{bps}. This may indicate |
|---|
| | that the level of selection difficulty in our experiment is higher than |
|---|
| | in previous research. This could be due to the selection of GUI targets |
|---|
| | instead of arbitrary rectangular targets. |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Error rate} |
|---|
| | \label{sec-results-error-rate} |
|---|
| | |
|---|
| | The average error rate for the mouse was only 2.7\% which is consistent |
|---|
| | with previous studies. The touch screen overlay, on the other hand, had |
|---|
| | an average error rate of 60.8\%. \citet{Sear-A-1991-IJMMS} found that a |
|---|
| | touch screen monitor had an average error rate of 49\% but this was |
|---|
| | across much smaller targets. This suggests that there is a loss of |
|---|
| | accuracy when using a touch screen overlay as opposed to a touch screen |
|---|
| | monitor. |
|---|
| | |
|---|
| | The check box had a significantly high average error rate of 78.5\% |
|---|
| | across all sizes and both devices; in particular, the small check box on |
|---|
| | the touch screen overlay had an error rate of 393\%. The touch screen |
|---|
| | overlay incurred the majority of the errors. For all sizes of the check |
|---|
| | box the mouse produced an average error rate of 6.7\%, while the touch |
|---|
| | screen overlay produced an average error rate of 178.5\%. The |
|---|
| | distinguishing factor of the check box compared to the other target |
|---|
| | types is its small size, so we can conclude from this that a touch |
|---|
| | screen overlay is more inaccurate for selecting small targets |
|---|
| | (\unit[4]{mm} or less). |
|---|
| | |
|---|
| | The button and text box had much lower error rates than the check box |
|---|
| | and combo box (as seen in Figure~\ref{fig-error-rate}). As the button |
|---|
| | and text box also exhibited low movement times, we can conclude that |
|---|
| | these two target types have very good overall performance. |
|---|
| | |
|---|
| | |
|---|
| | \begin{figure} |
|---|
| | \centering |
|---|
| | \includegraphics{error-rate} |
|---|
| | \caption{Error rate by target type and device, averaged across all |
|---|
| | target sizes.} |
|---|
| | \label{fig-error-rate} |
|---|
| | \end{figure} |
|---|
| | |
|---|
| | |
|---|
| | Note that the error rate calculation for combo boxes assumes a |
|---|
| | ``two-click'' selection approach, as only two of the twenty-four |
|---|
| | participants used the ``one-click'' approach. Both of these participants |
|---|
| | used the mouse. |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Comfort} |
|---|
| | \label{sec-results-comfort} |
|---|
| | |
|---|
| | In terms of accurate pointing the mouse (2.083) was rated easier than |
|---|
| | the touch screen overlay (3.000). These differences were statistically |
|---|
| | significant \((p < 0.01)\). The responses regarding the question on |
|---|
| | neck, wrist and arm fatigue showed that the touch screen overlay had a |
|---|
| | high rating (4.083), whereas the mouse was rated in the midpoint range |
|---|
| | (3.167). These differences were statistically significant \((p < 0.05)\). |
|---|
| | The final question rated the overall difficulty in using the selection |
|---|
| | device. The mouse (4.250) was rated easier to use than the touch screen |
|---|
| | overlay (3.333). These differences were statistically significant \((p < |
|---|
| | 0.05)\). |
|---|
| | |
|---|
| | Participants using the touch screen overlay rated both the text box and |
|---|
| | button as easy to accurately select, with the large and medium sizes |
|---|
| | being most preferred. This feedback is consistent with the data |
|---|
| | collected in that the text box and button have low movement times and |
|---|
| | low error rates (i.e., they are easy to accurately select). The combo |
|---|
| | box was rated in the middle of the range, and the check box was rated as |
|---|
| | very hard to select. Three quarters of the touch screen overlay |
|---|
| | participants preferred to select large combo boxes and check boxes, |
|---|
| | which is consistent with the high error rates and movement times |
|---|
| | associated with these two target types on the touch screen overlay. |
|---|
| | |
|---|
| | Participants using the mouse also rated the text box and button as easy |
|---|
| | to accurately select, with the large and medium sizes being most |
|---|
| | preferred. Both the combo box and check box were rated harder to select |
|---|
| | than the button and text box with the check box having the worst rating. |
|---|
| | As with the touch screen overlay, participants preferred large combo |
|---|
| | boxes and check boxes. |
|---|
| | |
|---|
| | In the general feedback, one participant noted the lack of arm support |
|---|
| | when selecting targets at the top of the screen. This is an interesting |
|---|
| | comment, because the nature of using a touch screen means the user's arm |
|---|
| | might be raised off the desk, and thus be self-supporting when selecting |
|---|
| | items towards the top of the screen. |
|---|
| | |
|---|
| | Another suggestion was making the target change colour when the cursor |
|---|
| | is located above it. This is a similar concept to that of interactive |
|---|
| | rollover items commonly used in web pages. Auditory feedback has been |
|---|
| | shown to affect speed and accuracy when making a selection |
|---|
| | \citep{Bend-G-1999-PhD}, so it is likely that the visual feedback |
|---|
| | received from GUI targets will affect the selection performance. All of |
|---|
| | the target types tested provide some form of immediate visual feedback, |
|---|
| | from the button being visually depressed to a tick appearing in the |
|---|
| | check box. Further study is needed to assess how visual feedback affects |
|---|
| | selection performance of GUI items and what is the most effective method of |
|---|
| | providing feedback. |
|---|
| | |
|---|
| | |
|---|
| | \subsection{Other findings} |
|---|
| | \label{sec-results-other} |
|---|
| | |
|---|
| | Two interesting patterns emerged when we calculated the standard |
|---|
| | deviation of the final selection coordinates on the screen. First, when |
|---|
| | selecting text boxes with the mouse, there was greater variation in |
|---|
| | final selection coordinates on the right side of the screen |
|---|
| | (\(45^{\circ}\) and \(315^{\circ}\) target angles) than on the left side |
|---|
| | of the screen (\(90^{\circ}\) and \(225^{\circ}\) target angles). This |
|---|
| | behaviour was not apparent when selecting text boxes with the touch |
|---|
| | screen overlay, as illustrated in Figure~\ref{fig-variation-textbox}. |
|---|
| | This would mean that participants using the mouse were more careful when |
|---|
| | making selections with text boxes on the left side of the screen than on |
|---|
| | the right. |
|---|
| | |
|---|
| | |
|---|
| | \begin{figure} |
|---|
| | \centering |
|---|
| | \includegraphics{variation-text-mouse} |
|---|
| | \includegraphics{variation-text-touch} |
|---|
| | \caption{Standard deviation of final selection coordinates for the |
|---|
| | text box, averaged across all target sizes.} |
|---|
| | \label{fig-variation-textbox} |
|---|
| | \end{figure} |
|---|
| | |
|---|
| | |
|---|
| | Second, and even more interesting, was the observation that while |
|---|
| | selections made on the combo box with the mouse exhibited similar |
|---|
| | behaviour to the text box, the behaviour on the touch screen overlay was |
|---|
| | the opposite (although less pronounced), as shown in |
|---|
| | Figure~\ref{fig-variation-combobox}. That is, selections of combo boxes |
|---|
| | on the left side of the touch screen overlay had greater variation than |
|---|
| | selections made on the right. |
|---|
| | |
|---|
| | |
|---|
| | \begin{figure} |
|---|
| | \centering |
|---|
| | \includegraphics{variation-combo-mouse} |
|---|
| | \includegraphics{variation-combo-touch} |
|---|
| | \caption{Standard deviation of final selection coordinates for the |
|---|
| | combo box, averaged across all target sizes.} |
|---|
| | \label{fig-variation-combobox} |
|---|
| | \end{figure} |
|---|
| | |
|---|
| | |
|---|
| | These effects were most pronounced for the large size of both the text |
|---|
| | box and the combo box. The variation of selection coordinates for the |
|---|
| | smaller targets (the button and check box) was consistent across both |
|---|
| | the mouse and touch screen overlay and for all target sizes. |
|---|
| | |
|---|
| | We can only speculate as to the reasons for this variation. In the case |
|---|
| | of the combo box, one possibility is its asymmetrical appearance |
|---|
| | compared to the other target types, which may encourage participants to |
|---|
| | try to click specifically on the drop-down arrow of the combo box, |
|---|
| | rather than treating the entire combo box as a target (this could also |
|---|
| | be another factor in the slow movement times for this target type). |
|---|
| | However, this does not explain the variation between left and right |
|---|
| | sides of the screen, nor why the same behaviour was observed with the |
|---|
| | completely symmetrical text box. |
|---|
| | |
|---|
| | Another possibility is the handedness of the participants, which in the |
|---|
| | case of a touch screen might affect how difficult it is to select |
|---|
| | targets on different sides of the screen. Unfortunately we did not ask |
|---|
| | participants whether they were right- or left-handed, and thus can draw |
|---|
| | no conclusions on this point. |
|---|
| | |
|---|
| | |
|---|
| | \section{Conclusion} |
|---|
| | \label{sec-conclusions} |
|---|
| | |
|---|
| | The goal of our study was to assess the efficacy of a touch screen |
|---|
| | overlay compared to a mouse, when selecting the typical GUI targets |
|---|
| | commonly presented to users in desktop information systems. This was |
|---|
| | achieved by an experiment measuring movement time, throughput and error |
|---|
| | rate for various combinations of target type, size, angle and distance. |
|---|
| | Comfort and user satisfaction were assessed by means of a questionnaire. |
|---|
| | |
|---|
| | The results showed that the touch screen overlay was both slower and |
|---|
| | less accurate than the mouse. The touch screen overlay was found to have |
|---|
| | reasonable performance with large GUI items but poor performance with |
|---|
| | smaller GUI items. The touch screen overlay did have comparable movement |
|---|
| | times to the mouse for medium and large sized targets. Throughput did |
|---|
| | not vary across device or target size but did vary across target type. |
|---|
| | Both selection devices had the same user preference except with respect |
|---|
| | to the smallest target type (check boxes), in which the mouse had a |
|---|
| | higher preference. The mouse was rated easier to make accurate |
|---|
| | selections with than the touch screen overlay. The touch screen overlay |
|---|
| | also had worse arm, wrist and finger fatigue compared to the mouse. From |
|---|
| | these results we can conclude that the mouse had higher user |
|---|
| | satisfaction than a touch screen. |
|---|
| | |
|---|
| | An unusual variation in final selection coordinates was noted for both |
|---|
| | text boxes and combo boxes. Further studies are required to establish |
|---|
| | why this variation occurs. |
|---|
| | |
|---|
| | In general we can conclude that a touch screen overlay with no external |
|---|
| | device (e.g., a pen) is not an effective selection device for targets |
|---|
| | with dimensions of \unit[4]{mm} or smaller. When designing interfaces |
|---|
| | that will be used with a touch screen overlay, selection within the |
|---|
| | interface will be more efficient if the GUI items are larger than |
|---|
| | \unit[4]{mm}. |
|---|
| | |
|---|
| | Although the results showed that the touch screen overlay was not |
|---|
| | efficient and usable for selecting GUI items with a size of \unit[4]{mm} |
|---|
| | or less, this may not be the case when a pen or some external device is |
|---|
| | used in conjunction with the touch screen overlay. In general there |
|---|
| | seems to be a lack of research in device assessment of touch screen |
|---|
| | overlays with pens or other external devices. Further testing on touch |
|---|
| | screen overlays used with an external device such as a pen may well show |
|---|
| | that a touch screen overlay is adequate and efficient for selecting |
|---|
| | small GUI items. |
|---|
| | |
|---|
| | |
|---|
| | % The Appendices part is started with the command \appendix; |
|---|
| | % appendix sections are then done as normal sections |
|---|
| | % \appendix |
|---|
| | |
|---|
| | % \section{} |
|---|
| | % \label{} |
|---|
| | |
|---|
| | % Bibliographic references with the natbib package: |
|---|
| | % Parenthetical: \citep{Bai92} produces (Bailyn 1992). |
|---|
| | % Textual: \citet{Bai95} produces Bailyn et al. (1995). |
|---|
| | % An affix and part of a reference: |
|---|
| | % \citep[e.g.][Ch. 2]{Bar76} |
|---|
| | % produces (e.g. Barnes et al. 1976, Ch. 2). |
|---|
| | |
|---|
| | \bibliographystyle{elsart-harv} |
|---|
| | \bibliography{Gleeson_paper} |
|---|
| | % \begin{thebibliography}{} |
|---|
| | |
|---|
| | % \bibitem[Names(Year)]{label} or \bibitem[Names(Year)Long names]{label}. |
|---|
| | % (\harvarditem{Name}{Year}{label} is also supported.) |
|---|
| | % Text of bibliographic item |
|---|
| | |
|---|
| | % \bibitem[]{} |
|---|
| | % |
|---|
| | % \end{thebibliography} |
|---|
| | |
|---|
| | \end{document} |
|---|
| | |
|---|
| | |
|---|
