Class 6, June 13th, 2000 Product Recommendation

Transcript

145 Class 6, June 13th, 2000 146 Class 6, June 13th, 2000 Tuesday, June 13th, 2000 Human-Computer Interface Design, Introductory Course 1 credit, third trimester, second module 1999/2000 1. Questions and Quiz 2. Comparison of Product Recommendation Techniques 3. Principles to Support Usability Discussed with reference to a familiar system 4. Final Exam from Spring, 1999 5. Final Exam from Fall, 1999 Product Recommendation Techniques Collaborative Filtering: Basic Idea SIMILARITY TO PARTICULAR OTHER USERS COMPUTATION OF CORRELATIONS WITH OTHER USERS’ RATINGS U’S RATINGS OF OBJECTS WEIGHTED AVERAGING OF RATINGS OF OTHERS PREDICTED RATINGS OF U 146 Course Web page: http://www.cs.uni-sb.de/users/jameson/hcid/ 145 147 Product Recommendation Techniques 148 Instructions As we look for examples in the Web, make notes on examples of the following concepts Recommendation technologies People-to-people correlation (= Collaborative filtering) Item-to-item correlation Attribute-based recommendation Aggregated ranking Examples of Concepts (2) Ways for U to find recommendations Engage in organic navigation Request a recommendation list Supply keywords or freeform input Select options that define recommendations 148 These concepts are discussed in: Schafer, J. B., Konstan, J., & Riedl, J. (1999). Recommender systems in e-commerce. Proceedings of the ACM Conference on Electronic Commerce. (http://www.cs.umn.edu/Research/GroupLens/) Examples of Concepts (1) 147 149 149 Product Recommendation Techniques 150 Examples of Concepts (3) Time scale of recommendations Persistent system Ephemeral system Effort required from U Automatic recommendation Manually controlled recommendation Applying Usability Principles to S Predictability • Can U predict the effects of his actions on the basis of experience with previous actions? • Can U at any moment determine what actions can be performed? (operation visibility) Synthesizability • Can U perceive and understand the effects of his actions on the system state? • Are the effects of U’s actions immediately perceivable or only after U has taken special steps to perceive them (immediate vs. eventual honesty)? 150 The formulation of these principles is adapted from Dix et al. (1998), which in turn adapted many of the principles from previous works. Principles Concerning Learnability (1) 151 151 Applying Usability Principles to S 152 Principles Concerning Learnability (2) Familiarity • Can U exploit his prior knowledge when learning to use S? • Do the properties of objects in S suggest what can be done with them (affordances)? Generalizability • Once U has learned how to achieve a specific goal with S, can he use similar methods to achieve similar goals - either with S or with other systems? Principles Concerning Learnability (3) Consistency • Can the behavior of S - and the actions that U needs to perform with S - described in terms of a small number of general rules, or does U have to learn a lot of specific rules and exceptions? (Note: Consistency can arise at many levels and take many different forms) 152 153 153 Applying Usability Principles to S 154 Principles Concerning Flexibility (1) Dialogue initiative • Can U initiate an action whenever it makes sense for him to do so? Multithreading • Can U switch very quickly between tasks (interleaving)? • Can U even send or receive two messages at the same moment (concurrency)? Task migratability • Can U pass control over task execution to S - or take control from S - as appropriate in the given situation? Principles Concerning Flexibility (2) Substitutivity • Can U choose between different ways of inputing a given piece of information to S? • Is S capable of presenting a given piece of information to U in different ways? • Can U use S’s output when specifying his input (equal opportunity)? Customizability • Can U adapt aspects of S to suit his own preferences or needs (adaptability)? • Does S automatically adapt aspects of its behavior to U (adaptivity)? 154 155 155 Applying Usability Principles to S 156 Principles Concerning Robustness (1) Observability • Can U find out what he needs to know about the state of S - without disturbing that state (browsability)? • Does S explicitly offer U defaults, reducing U’s need to recall and specify actions? • Can U still perceive some reminder of a change in S’s state some time after the change has occurred (persistence)? Recoverability • Can U easily return to a desired previous system state (e.g., after an error)? Principles Concerning Robustness (2) Responsiveness • Can U perceive changes in S’s state immediately after they occur (in particular, immediately after U has given an input)? • If not, can U at least perceive immediately that S is responding in some way to a change? Task conformance • Can U perform all of the tasks he wants to perform with S (task completeness)? • Can U perform his tasks in a natural way, given his own understanding of the tasks (task adequacy)? 156 157 Exam 1: EarthTime User’s Guide 158 Exam 1: EarthTime User’s Guide 157 Running the Program Just tap on the icon to start the program. You should see something like this: Setting the "Home" Timezone The first thing you need to do is set which timezone is the "home" timezone. The "home" timezone is typically the one where you live. Technically, it is the timezone whose time matches your PalmPilot’s system time. To do this tap on the "Home" radio button (just above "Curr"). When the "Home" radio button is highlighted the program is in a special mode to accept a new home timezone. Now tap on the map of the world, and select your home timezone. When you have done this, tap the "Curr" radio button, to put the program back in normal mode. 158 159 159 Exam 1: EarthTime User’s Guide 160 Daylight Savings Time If your home timezone is in DST (Daylight Savings Time), tap on the little sun icon on the same row as the "Home" radio button. When the icon is black, DST is OFF. When the icon is unfilled (white), DST is ON (i.e., Summer time). Querying Times Using the Map Make sure the mode is set to "Curr", i.e., the Home/Curr radio buttons should have "Curr" filled black. Simply tap on the map, or drag the pen around and you will see the timezone drawn on the map, and the time in that zone displayed to the right of the "Curr" radio button. If the zone you are querying is in Summer time, i.e., DST, tap on the little sun icon on the same row as the "Curr" radio button so that it becomes unfilled (white). Tapping the sun icon toggles between ON and OFF. 160 161 161 Exam 1: EarthTime User’s Guide Changing the City Times Simply tap on the names to pop up a list of defined cities. Scroll the list up and down and then tap on the one desired. Again, you can tap the little sun icons to toggle DST on/off for that city. 162 163 163 Exam 1: EarthTime User’s Guide 164 "What-If?" Times (1) If you want to know what time it would be in one zone when it is, say 3 pm, in another zone (like the home timezone) you can do this by using EarthTime’s "hypothetical mode". First, tap on the "Other" radio button in the top-right corner of the screen. The program is now in "hypothetical mode". The program now switches over to a completely separate configuration. You can set the home timezone, like you did before. This doesn’t change your real home setting, just the hypothetical one. "What-If?" Times (2) Tap on the "Set" button (just under the map, to the right) to set the HOME timezone’s hypothetical time (i.e., the imaginary time). Once set, make sure the "Curr" radio button is selected, and use the program just like when it’s in normal mode. All the times displayed are what the times would be if the home time was as you set it. Tap on the "Now" radio button near the top-right to put the program back into the normal mode. 164 165 Exam 1: Instructions 166 Exam 1: Instructions Overall Question 165 Note These instructions are identical to those that were distributed earlier Overall question The overall question to you is "What would you write in an e-mail message to this designer in order to help her better to understand the issues she’s been thinking about?" You can offer • Possible explanations of phenomena that the designer has observed (e.g. typical user difficulties) • Suggestions as to how S might be improved Goals 166 Goals in formulating an answer 1. Say things that are useful and relevant to the issues that D has raised That is, don’t just mention ideas from the book or your notes without making it clear why they are relevant to D’s concerns 2. Show that you have learned something in this course That is, you must resist the temptation to express ideas that have no clear relationship to the material of this course, no matter how brilliant such ideas may be 3. Don’t bother to define or explain concepts to D Assume that D is already familiar with the material of the course (We make this assumption because it would be trivial and time-consuming, in an open-book exam, to repeat ideas that are explained in the book or on the slides) 167 Exam 1: Instructions 168 Grading 167 Grading principles The contributions that you make will be evaluated in terms of their quality, relevance, and quantity (i.e., it’s better to express a lot of good ideas than just a couple) The maximum number of N points [N depends on the particular course] will be assigned if the writer shows an excellent understanding of the course material and an ability to apply it to real problems 169 Exam 1: Comments by the Designer 170 Exam 1: Comments by the Designer 169 Errors? (1) It seems that users sometimes change the "Home" zone even though they think they’re just changing the "Current" zone. I actually thought I’d given enough information to help them avoid this mistake. When they’re in "Home" mode, the house at the top of the screen moves. Also, the word "Home" in the lower part of the screen is highlighted. Errors? (2) Still, maybe it would help if they used different gestures to specify the "Home" and "Current" zones. Then maybe the two modes wouldn’t be necessary. I wonder if the system offers any other unnecessary possibilities for errors; and how the design might be changed to prevent them. 170 171 171 Exam 1: Comments by the Designer 172 Cities menu (1) The menu with all of the cities can get quite large, since there is an optional database with about 200 cities. So U may have to scroll for a while before reaching a city near the end of the alphabet. I suppose the menu could be broken up into a hierarchy of menus in some way. But I seem to recall a guideline that says that, with alphabetically ordered menu items, it’s best to put as many items as possible on a single level of the menu. Cities menu (2) Within the menu, I tried to present a lot of useful information in a clear format (timezone relative to Greenwich Mean Time; country code and area code for phoning) Some people seem to find the list a bit confusing, though. I thought it would be useful to give the country code and area code for phoning in the list. This way, when making a call to another city, they can see what time it is there and also see the first part of the phone number. But I sometimes wonder if they can remember all that information anyway while they’re preparing the call. 172 173 173 Exam 1: Comments by the Designer 174 The World Map Since I could use only black and white, it wasn’t easy to mark the selected time zone so that it stands out clearly from the rest. Noticing which zone is selected seems easiest if you drag the stylus across the screen instead of just tapping at one point. Sometimes users want to remember where a given timezone is (e.g., so that they can quickly select Moscow’s zone if they have to call Moscow frequently). I wonder if there’s anything I should do or not do - to make this remembering as easy as possible. The Rest of the Main Screen I’m not sure it’s clear enough which of the buttons "Now" and "Other" in the top right is selected at any given moment; and similarly for "Home" and "Curr" at the bottom left. Does black mean "selected" or "not selected"? The problem also arises with the suns that are used to represent Daylight Savings Time. Here, I hoped that users could use the memory aid "light" = "sunshine" = "summertime". I think I did a pretty good job of arranging the information in the bottom part of the screen, though. 174 175 175 Exam 1: Comments by the Designer 176 More Powerful Interaction Techniques? I’m planning to make a version of EarthTime for laptop computers. I plan to keep the same basic structure, but I’d like to take advantage of modern interaction techniques. For example, maybe color, 3D drawings, or sound could be used to make interaction with the world map more understandable. A more radical idea would be to allow users to type (or even speak) queries in normal English. E.g., "What time will it be here in Bruchsal when it’s 8 am in Sydney tomorrow morning?" But I don’t know if this is a sensible use of natural language interaction. Ubiquitous Computing? I suppose this program is an example of "ubiquitous computing", since it’s for people who are traveling all over the world. But I don’t know what ideas from the ubiquitous computing paradigm could be relevant to improving the design of EarthTime. 176 177 177 Exam 1: Comments by the Designer 178 Modes and Mental Models (1) Any comments on the issues on this and the next slide are for extra credit (maximum of 5 points). An important distinction is the one between the "Home" and the "Current" (Curr) timezones When giving them these names, I was thinking of the following situation: U has set the "Home" timezone to the one where he lives. U is now flying around the world and wants to check repeatedly what time it is in the timezone that he is currently in - without bothering to reset the system clock. U also wants to check occasionally what time it is back home. Modes and Mental Models (2) 178 The names are less appropriate for other situations, e.g.: U is visiting Moscow and wants to call a lot of people around the world from there, so he makes Moscow’s timezone the "Home" zone. To see what time it is in another zone, he makes that zone the "current" zone, even though it’s not really "current" for him. So maybe I should just call them something like the "System Timezone" and the "Query Timezone". But I thought that people aren’t good at reasoning with abstract concepts, so I used these familiar concepts, even though they are inaccurate in most cases. It would be nice to come up with a metaphor that would help to make this distinction clearer. Similarly, I suspect the difference between "Now" and "Other" modes could be made clearer; but I don’t really know how. 179 Exam 1: Summary of Student Answers 180 Exam 1: Summary of Student Answers 179 Errors? (1) Making a change while in the wrong mode is a context error Ways to help distinguish the modes: • Make the house flash, so that it will be noticed even with peripheral vision • Surround the house with a jagged boundary to make it preattentively distinguishable from the rest of the map • Swap black and white in the map when changing modes • Have an extra label appear next to the bar while it’s being moved • Ask for confirmation after every change (?) Errors? (2) 180 U may forget to switch back into "Now" mode after making a change in "Other" mode, because making the change gives a feeling of closure The same applies to "Curr" and "Home" modes So task migration may be desirable here: S switches automatically back to the more frequently used mode after a certain delay The required skills will only become compiled and automatic if U uses S frequently 181 Exam 1: Summary of Student Answers 182 Cities Menu (1) 181 Hierarchy Search time per level would be logarithmic if scrolling weren’t required Because of scrolling, it’s closer to being linear So a deeper hierarchy would save time by making the overall time function logarithmic Possible first levels: • First letter of city name • Continent Cities Menu (2) 182 Additional information The two columns on the right are not preattentively distinguishable They should be arranged so that they form spatially coherent groups Labels or icons at the top could show what the columns mean U may need to use short-term or sensory memory to take advantage of the numerical timezone information, since the world map is partly covered by the cities menu 183 183 Exam 1: Summary of Student Answers 184 World Map / Rest of the Main Screen The bold type for the three cities at the bottom makes them seem similar to the selected buttons "The mind judges a book by its cover" Using black for selected modes is inconsistent with using white for Daylight Savings Time But it’s consistent with using black to highlight the program name at the top of the screen More Powerful Interaction Techniques? (1) Natural language Problems Different native languages, accents, background noise ... Inherent ambiguity and context-dependence of natural language Speech output is not persistent, so it is harder to integrate several pieces of information Positive aspects Speech would make S more accessible to some users with disabilities The limited domain of discourse makes interpretation easier 184 185 Exam 1: Summary of Student Answers 186 More Powerful Interaction Techniques? (2) 185 Nonspeech sound Earcons or auditory icons could help to distinguish between modes by offering differing auditory feedback on actions 3D A 3D world map could make it easier for U to recognize and recall time zones 3D buttons could be more easily recognized as having being pressed or not pressed Color Color would make it easier to distinguish between selected and nonselected modes Some countries could be coded with colors associated with them Ubiquitous Computing? Negative aspects The PDA is not unobtrusive; it doesn’t blend smoothly into the environment Positive aspects S runs on a mobile device S could use GPS technology to detect U’s position automatically (context-awareness) 186 187 187 Exam 1: Summary of Student Answers Modes and Mental Models Terms should be familiar and clearly suggest what they are supposed to mean "Browse mode": U can explore various times without changing the real time 188 189 Exam 2: Introduction to ClockPro 190 Exam 2: Introduction to ClockPro 189 Overall Design (1) ClockPro has three independent pages: Clock, Timer and Alarm. You can switch these pages by tapping the tabs. Each independent page can be configured in the Options menu and by tapping icons and digits on the screen. Tap icons and small digits to show/hide them. What is displayed on the big digits? It is your system time on Clock page, last timer lap on Timer page and time to alarm on Alarm page. Overall Design (2) Can I turn off these frames and outlines? Sure. They are here to help you locate the inactive icons and digits. If you do not like them, go to Options / General menu and choose "none" or "icons" in Outline controls list. 190 191 191 Exam 2: Introduction to ClockPro 192 Alarm Page (1) Why are the numbers on Alarm page counting backwards? The big digits on Alarm page show how much time until alarm goes off. In ClockPro, the alarm is set to some time (’Set Alarm to’ rectangle in Alarm settings) even if you do not have any notification on (sound, info screen, backlight). This allows you to see how much time left you have until meeting, how much more your flight will last etc. without the need to hear the sound when the alarm goes off. Alarm Page (2) What are the three upper left hand icons? They control the notification for each page. ... On the Alarm page they determine what happens when alarm comes off. There are three types of notification: Bell icon: Sound notification. You can choose what sound you want to hear .... (Light bulb icon: Backlight blinking....). (Screen icon: Screen with written information ....) Other icons Speaker: Turns on audible ticking (once every second) for each page. Lock: Disables auto-off while in ClockPro (Auto-off: The device turns itself off automatically after a certain interval) 192 193 193 Exam 2: Introduction to ClockPro 194 Setting the Alarm (1) Double tap the Alarm tab to get to alarm setting dialog. Choose a time format. HH:MM ss: Big digits on main screen show hours and minutes, small digits show seconds (can be hidden) MM:SS hh: Big digits on main screen show minutes and seconds, small digits show hours (can be hidden) Setting the Alarm (2) Then tap the ’Set Alarm to’ rectangle and set the desired time. Tap upper or lower part of each digit to increase or decrease its value. Choose the days of the week on the ’repeated’ bar. The alarm will only go off on the selected days 194 195 195 Exam 2: Introduction to ClockPro 196 Setting the Alarm (3) Sound: Choose a sound and set how many times you want the sound to be repeated. You can stop any playing sound/light and snooze or discard an alarm by pressing the hardware buttons. To turn alarm sound / light / screen on or off you have to choose the appropriate icons on the main Alarm screen. Setting the Alarm (4) 196 Snooze time: Set a time period for snooze. If you do not press any button during the alarm sound, the alarm will be snoozed automatically. Setting the snooze time to zero will disable the auto snooze feature. You can also snooze by pressing PageUp/Down hardware button or you can discard an alarm by pressing one of the 4 application hardware buttons. Play Snooze sound: Check this box if you want to hear the confirmation sound whenever the alarm is snoozed automatically or manually by pressing the PageUp/Down buttons. 197 197 Exam 2: Introduction to ClockPro 198 Setting the Alarm (5) Press ’Ok’ button and check out you have the bell icon active on Alarm page. Auto preset: To prevent forgetting to turn on some way of chime/ timer/alarm notification choose what you want to preset automatically whenever you change any chime/timer/alarm related settings. When the Alarm Goes Off How do I shut off the sounds? Just press any hardware button (PageUp/Down or 4 application buttons) while the sound is playing. If the sound playing is produced by Alarm (not by Clock chiming or Timer expiration) you can choose whether you want to shut off the sound and snooze the alarm at the same time (then press PageUp/Down buttons) or whether you just want to shut off the alarm without snooze (then press one of the 4 application buttons). 198 199 Exam 2: Commets by the Designer 200 Exam 2: Commets by the Designer Setting the Alarm 199 Using previous experience? U needs to learn what steps to perform when setting an alarm I would hope that U’s experience in setting normal alarm clocks would help here Method for setting time I’m quite proud of my method for changing the digits while setting the alarm (by simply tapping on the top or bottom of a digit) Almost all other systems have more complex methods for setting a time E.g., you select a digit and then push on an upward or downward arrow icon to increase or decrease it I frankly think that every system should adopt my method instead of other pen input methods like these Of course, one could also consider completely different methods for inputing the time information Errors (1) 200 Specific known error One user U told me about the following error that he made while setting an alarm It was Monday evening, and he had already used the alarm page on Monday afternoon; so Monday was selected on the "Repeated" bar U set an alarm for Tuesday morning, 5:20 am He forgot to check Tuesday instead of Monday on the "Repeated" bar So the alarm was actually set to go off at 5:20 am the next Monday, so U overslept Of course I’d like to improve the design to prevent this type of error Note that S already gives a warning if an alarm is set but no day has been selected But S can’t give a warning if the wrong day is selected, since S can’t know which day U intends the alarm to go off on 201 Exam 2: Commets by the Designer 202 Errors (2) 201 Overlooking the snooze sound? When the alarm has gone off, it may be important that U notice whether the alarm will be snoozed (i.e., be repeated after a few minutes) That’s why I added the special "snooze" sound, which is heard when after the alarm has gone off (if the alarm will be snoozed) But I wonder what happens if U isn’t specifically listening to hear if the snooze sound will appear Other possible errors? I also wonder if there are any other types of error that users might tend to make, which I could prevent with a better design Automatic Processing; Real Alarm Clocks 202 Automatic processing I hope that U’s processing with ClockPro can become automatic after U has gained experience with the system I wonder what parts of the operation of S are likely to become automatic More like a real alarm clock? Some people have asked why I didn’t make ClockPro look and work more like a normal physical alarm clock (for example, the digital ones that a lot of people are familiar with) I never really tried to imitate a normal clock Should I try to do so more in the next version? 203 203 Exam 2: Commets by the Designer 204 Taking Human Limitations Into Account Visual perception I think I’ve done a good job of taking into account the limitations of human visual perception For example, even people who normally wear glasses say they can read the big digits when they wake up in the middle of the night to check the time I don’t think that ClockPro needs any improvement in this respect Working memory Also, I’ve tried to minimize the burden on U’s working memory But I wonder if I could do an even better job at this Screen Design and Direct Manipulation Screen design In both the main pages and the alarm-setting screen, I’ve tried to observe the basic principles of good screen design Frankly, I think I’ve done pretty well, and I wouldn’t know what to improve Direct manipulation I tried to make ClockPro a direct manipulation system in every respect I wonder if I could go even further in this direction 204 205 Exam 2: Summary of Student Answers 206 Exam 2: Summary of Student Answers 205 Setting the Alarm: Changing Digits (1) Method for setting time I’m quite proud of my method for changing the digits while setting the alarm (by simply tapping on the top or bottom of a digit) Almost all other systems have more complex methods for setting a time E.g., you select a digit and then push on an upward or downward arrow icon to increase or decrease it I frankly think that every system should adopt my method instead of other pen input methods like these Of course, one could also consider completely different methods for inputing the time information Setting the Alarm: Changing Digits (2) 206 Comments A new user would probably not know how to set the time unless he consulted the user support The method is inconsistent with the mental model that a user has of a digital watch or any other computer application So this method scores poorly in terms of the "familiarity" principle of learnability Tapping just one part of a digit might be slow in terms of Fitts’s Law [How big is the target that U has to tap according to other methods?] 207 207 Exam 2: Summary of Student Answers 208 Specific Known Error Specific known error One user U told me about the following error that he made while setting an alarm It was Monday evening, and he had already used the alarm page on Monday afternoon; so Monday was selected on the "Repeated" bar U set an alarm for Tuesday morning, 5:20 am He forgot to check Tuesday instead of Monday on the "Repeated" bar So the alarm was actually set to go off at 5:20 am the next Monday, so U overslept Of course I’d like to improve the design to prevent this type of error Note that S already gives a warning if an alarm is set but no day has been selected But S can’t give a warning if the wrong day is selected, since S can’t know which day U intends the alarm to go off on Specific Known Error: Comments (1) 208 This error is a context error U made an incorrect assumption about the current context [Which assumption, exactly?] Possible remedy Provide a visible message on the screen confirming the setting [On what screen, at what time?] This error is also a description error Because all of the day icons look similar Blackening the selected day makes it preattentively distinguishable But "Tuesday" and "Thursday" look basically identical Remedy: Use "Tu" and "Th" 209 209 Exam 2: Summary of Student Answers 210 Specific Known Error: Comments (2) The problem is that S processes whatever inputs it gets, without checking its plausibility By contrast, for humans "the mind is not a camera" Remedy: Give a message confirming which day was chosen This message could be annoying sometimes, but it could avoid some important appointments being missed There are actually two problems: forgetting to click a day at all, and clicking the wrong day Possible remedies for both problems Have a (larger) day menu automatically pop up Have the day selected within the time setting menu [Would this help with the first problem?] Speech feedback could help prevent the error "You have selected Monday" [Why is this type of feedback especially suitable?] Overlooking the Snooze Sound (1) Overlooking the snooze sound? 210 When the alarm has gone off, it may be important that U notice whether the alarm will be snoozed (i.e., be repeated after a few minutes) That’s why I added the special "snooze" sound, which is heard when after the alarm has gone off (if the alarm will be snoozed) But I wonder what happens if U isn’t specifically listening to hear if the snooze sound will appear Comments When U is not near the device when it goes off, he can’t hear the alarm or the snooze sound Remedy: S can have the snooze time blick on the screen until U has noticed it and turned the blinking off 211 211 Exam 2: Summary of Student Answers 212 Overlooking the Snooze Sound (2) Comments (continued) Even if U isn’t paying attention, the alarm and snooze sounds will be stored briefly in echoic memory So U will still be able to figure out what happened Similarly, in principle iconic memory could have been exploited in connection with visual feedback For example, if the day of the week for the alarm has been changed, S might blink the day display U could then more easily check if the change was correct The snooze sound may not be distinctive enough to catch U’s attention if he’s busy with some task A speech output message might be more effective [This would be an example of an auditory message that’s preattentively distinguishable] Other Possible Errors (1) 212 Other possible errors? I also wonder if there are any other types of error that users might tend to make, which I could prevent with a better design Comments "Forgetting an action" is also possible: Forgetting to set an audible alarm Remedy: Visible message [what, when?] U might enter the time in MM:HH:SS format, even though S interprets it as HH:MM:SS In other words, S’s flexibility in terms of formats can lead to errors by U [What type of error would this be?] 213 Exam 2: Summary of Student Answers 214 Other Possible Errors (2) 213 Comments (continued) It might be better to ask U, after he’s set the alarm, what sort of notification he wants to get [Why might this be better than just allowing U to set a general default notification?] U might press the wrong button when turning off the alarm, since they look quite similar This would be a [description] error [Actually, only the similar buttons have the same function in ClockPro] Automatic Processing 214 Automatic processing I hope that U’s processing with ClockPro can become automatic after U has gained experience with the system I wonder what parts of the operation of S are likely to become automatic Comments Automatic processing would reduce reliance on conscious control and working memory But it could lead to capture errors [and other expert slips] Which ones? [There were also summaries of what automatic processing involves, without indications of where it might occur in the use of ClockPro] 215 215 Exam 2: Summary of Student Answers 216 Setting the Alarm: Previous Experience (1) Using previous experience? U needs to learn what steps to perform when setting an alarm I would hope that U’s experience in setting normal alarm clocks would help here Comments In doing so, D is exploiting the principle of familiarity within the group learnability Some novel features of S are not covered by previous experience E.g., being able to set an alarm more than 24 hours ahead of time Setting the Alarm: Previous Experience (2) 216 Comments (continued) A "normal" alarm clock is not digital but analog [Whether this is true may depend on the background of U] So U will have difficulty in applying his previous experience to ClockPro D might consider adding a mode that imitates an analog alarm clock This mode would be quite different from the present system But users could make better use of it The present alarm-setting interface resembles a Windows dialog box more than a normal alarm clock So U should be able to make use of experience with Windows applications 217 217 Exam 2: Summary of Student Answers 218 Real Alarm Clocks More like a real alarm clock? Some people have asked why I didn’t make ClockPro look and work more like a normal physical alarm clock (for example, the digital ones that a lot of people are familiar with) I never really tried to imitate a normal clock Should I try to do so more in the next version? Comments Pros and cons of the alarm clock metaphor − Might raise false expectations − Might lead to restricted functionality + Supports formation of mental model Consequences of a mental model This model helps U to predict what will happen when U performs an action Note that mental models typically change over time, so U’s model should become more accurate over time Taking Human Limitations Into Account (1) 218 Visual perception I think I’ve done a good job of taking into account the limitations of human visual perception For example, even people who normally wear glasses say they can read the big digits when they wake up in the middle of the night to check the time I don’t think that ClockPro needs any improvement in this respect Comments D has in fact ensured appropriate luminance of the background and appropriate contrast between background and foreground D also took into account the limitation in people’s ability to process a lot of stimuli within a small space [Exactly what limitation is involved here?] By allowing U to hide some of the icons, D has ensure that U need not be confronted with too many stimuli on the screen 219 219 Exam 2: Summary of Student Answers 220 Taking Human Limitations Into Account (2) Working memory Also, I’ve tried to minimize the burden on U’s working memory But I wonder if I could do an even better job at this Comments The problem of premature closure can arise U sets the alarm time and feels that he is done But he may have forgotten to adjust the day or to request audible notification Remedy: Message asking U to check if everything has been set as desired Working memory would be burdened more if U had to perform calculations or remember events for short periods Shutting off the alarm puts a big burden on working memory U has to decide whether to allow the snooze or not, and he has to remember which corresponding button to press Actually, long-term memory is burdened more than working memory U has to remember a lot of details about the procedures Screen Design (1) 220 Screen design In both the main pages and the alarm-setting screen, I’ve tried to observe the basic principles of good screen design Frankly, I think I’ve done pretty well, and I wouldn’t know what to improve Comments Positive aspects Icons and text are combined in an appropriate way Icons with similar functions are grouped together Possible uses of color Make particular objects and actions preattentively distinguishable For example, use different colors (or fonts, etc.) for digital parts of the display that have different meanings [What could be the purposes of doing so?] 221 Exam 2: Summary of Student Answers 222 Screen Design (2) 221 Negative aspects The screens are far from beautiful The aesthetics could be improved with 3D effects, shadows, and colors Inconsistency In the alarm page, the big digits count downwards In the clock page, they count upwards [What problems could this inconsistency cause?] Some icons at the edges of the screen are not preattentively distinguishable So D might want to make them flash, for example [Which icons (if any) should be preattentively distinguishable?] Some of the terms used may not be correctly interpreted by the new user E.g., "Repeated", "Snooze" Similarly, some icons could be replaced by more self-explanatory ones Direct Manipulation Direct manipulation I tried to make ClockPro a direct manipulation system in every respect I wonder if I could go even further in this direction Comments Features typical of direct manipulation • No command entry • Objects visible on screen • Immediate visual feedback on actions • Reversibility of actions E.g., just click another icon to choose a different type of notification Possible improvements Purely digital aspects of the display could be supplemented with icons indicating their function E.g., an alarm-clock icon next to the big digits in the alarm clock page 222