User Interface Design and Ergonomics - National Open University of ...

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speed whenever the average load was low over a 20 minute period, with a similar prompt for high speed. 3.1.2 ACTION ANALYSIS Action analysis is an evaluation procedure that forces you to take a close look at the sequence of actions a user has to perform to complete a task with an interface. In this unit, we will distinguish between two flavors of action analysis. The first, "formal" action analysis, is often called "keystroke-level analysis" in HCI work. The formal approach is characterized by the extreme detail of the evaluation. The detail is so fine that, in many cases, the analysis can predict the time to complete tasks within a 20 percent margin of error, even before the interface is prototyped. It may also predict how long it will take a user to learn the interface. Unfortunately, formal action analysis is not easy to do. The second flavor of action analysis is what we call the "back of the envelope" approach. This kind of evaluation will not provide the detailed predictions of task time and interface learnability, but it can reveal large-scale problems that might otherwise get lost in the forest of details that a designer is faced with. As its name implies, the back-of- theenvelope approach does not take a lot of effort. Action analysis, whether formal or back-of-the-envelope, has two fundamental phases. The first phase is to decide what physical and mental steps a user will perform to complete one or more tasks with the interface. The second phase is to analyze those steps, looking for problems. Problems that the analysis might reveal are that it takes too many steps to perform a simple task, or it takes too long to perform the task, or there is too much to learn about the interface. The analysis might also reveal "holes" in the interface description -- things that the system should be able to do but can not. And it could be useful in writing or checking documentation, which should describe the facts and procedures that the analysis has shown the user needs to know. a. Formal Action Analysis The formal approach to action analysis has been used to make accurate predictions of the time it takes a skilled user to complete tasks. To predict task times, the times to perform each small step of the task, physical or mental, are estimated, and those times are totalled. Most steps take only a fraction of a second. A typical step is a keystroke, which is why the formal approach is often called "keystroke- level analysis." The predictions of times for each small step are found by testing hundreds of individual users, thousands of individual actions, and then calculating average values. These values have been determined for most of the common actions that users perform with computer interfaces. We summarize those values in the tables below. If an interface control is not in the table, it might be possible to extrapolate a reasonable value from similar devices, or user testing might have to be done for the new control. The procedure for developing the list of individual steps is very much like programming a computer. The basic task is divided into a few subtasks, like subroutines in a computer 168
program. Then each of those subtasks is broken into smaller subtasks, and so on until the description reaches the level of the fraction-of-a-second operations listed in the table. The end result is a hierarchical description of a task and the action sequence needed to accomplish it. 169
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] NATIONAL OPEN UNIVERSITY OF NIGER
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National Open University of Nigeria
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Summary ...........................
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UNIT 3 - GRAPHICAL USER INTERFACE (
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Assignments File Tutor-Marked Assig
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2 DESIGN and DESIGNING GOOD USER IN
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need both the study unit you are wo
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CIT 711: USER INTERFACE DESIGN AND
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UNIT 1 FUNDAMENTALS OF USER INTERFA
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3.3 TYPES OF USER INTERFACES Curren
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3.5 USER INTERFACE MODALITIES AND M
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Table of Contents 1.0 Introduction
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3.1.1 DESIGNING A GOOD USER INTERFA
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widgets properly is to read and und
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Figure 1:- Showing that alignment o
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6.0 TUTOR MARKED ASSIGNMENT a. How
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A graphical user interface is a typ
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Operating System. It is easy for a
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A list of items from which to selec
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collaborative work. For example, sc
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MODULE 1 UNIT 4 HUMAN COMPUTER INTE
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3.3 DIFFERNCES WITH RELATED FIELDS
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window blinds to automobile braking
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Wickens, Christopher D., John D. Le
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The International Ergonomics Associ
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approach, the Gilbreths reduced the
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3.6 BENEFITS OF ERGONOMICS The thre
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Another key to reducing lumbar disc
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MODULE 2 - USER INTERFACE DESIGN TE
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methods include inspection methods,
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Determine time of each operation (b
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unable to understand new informatio
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M cones, or, misleadingly, green co
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Motor skill which is a learned seri
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MODULE 2 UNIT 2 UNDERSTANDING USERS
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The users of a system must be ident
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This example brings up an important
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whether you want to have a palette
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Task analysis which includes identi
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MODULE 2 UNIT 3 USER CENTERED DESIG
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or small body text is also hard to
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Introduction to User-centered desig
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organizations themselves. Interacti
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After thorough analysis using vario
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Interaction design which is the dis
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In human-computer interaction and c
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The preferred method for ensuring u
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3.4 ISO STANDARDS FOR USABILITY ISO
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In this unit, you have been introdu
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affect the way the command is execu
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• Guides the user via the predefi
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The term direct manipulation was in
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There are two important reasons for
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UNIT 1 PROTOTYPING Table of Content
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Figure 12: The iterative steps of p
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select print Figure 13: An interfac
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Ambler, S.W. & Constantine, L.L. (2
Page 118 and 119: 3.2 LOW-FIDELITY PROTOTYPES Low-fid
Page 120 and 121: Figure 14:- Example of Sketching II
Page 122 and 123: Much more important for features th
Page 124 and 125: DENIM, an extension of SILK, is a t
Page 126 and 127: • Encourage menu & forms style, r
Page 128 and 129: Another problem is that native widg
Page 130 and 131: interfaces, so that a realistic sim
Page 132 and 133: UNIT 3 INPUT AND OUTPUT MODELS Tabl
Page 134 and 135: Recall that perceptual fusion means
Page 136 and 137: 3.2 OUTPUT MODEL There are basicall
Page 138 and 139: directly-mapped pixel image will no
Page 140 and 141: Most stroke models also include som
Page 142 and 143: UNIT 4 MODEL VIEW-CONTROLLER (MVC)
Page 144 and 145: 3.3.2 AS A DESIGN PATTERN MVC enco
Page 146 and 147: The Views are XForms controls for s
Page 148 and 149: UNIT 5 LAYOUTS AND CONSTRAINTS Tabl
Page 150 and 151: 3.5 CONSTRAINTS Constraints are rel
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Page 154 and 155: MODULE 4 UNIT 1 TECHNIQUES FOR EVAL
Page 156 and 157: a. Card Sorting Card sorting is a w
Page 158 and 159: Rapid prototyping is a method used
Page 160 and 161: 3.2.1 THE USE OF PROTOTYPES It is o
Page 162 and 163: Dumas, J.S. and Redish, J.C. (1999)
Page 164 and 165: the users' respect for you as a pro
Page 166 and 167: the users will be and what kind of
Page 170 and 171: Table 4:- Table: Average times for
Page 172 and 173: phases: list the actions, and then
Page 174 and 175: Nielsen and Molich used their own e
Page 176 and 177: 7.0 REFERENCES AND FURTHER READING
Page 178 and 179: users. If you do not, you can be ba
Page 180 and 181: If you are led to develop more and
Page 182 and 183: It's very easy to shape the comment
Page 184 and 185: a. Analyzing the Bottom-Line Number
Page 186 and 187: you use. But then you need some way
Page 188 and 189: ecruit test users with more similar
Page 190 and 191: MODULE 4 UNIT 4 OTHER EVALUATION IS
Page 192 and 193: 3.2 CURRENT ISSUES CONCERNING EVALU
Page 194 and 195: 2.0 OBJECTIVES By the end this unit
Page 196 and 197: It provides a real focal point for
Page 198 and 199: 3.3.4 CONDUCTING THE TEST Having co
Page 200: The stages involved in usability te
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