Homework 2 Anbang Xu 1. Thinking about user interface design. I have usually interacted with 3 non-desktop user interfaces as following: (a) (b) (c) Figure1. 3 of my non-desktop user interfaces (a) Cell Phone (b) Digital Television receiver (C) PDA. 1) Cell Phone The main function of my cell phone is communication. Recently, people like to communicate with others via Internet. So I think the most important feature in cell phone design is accessing Internet. Designers should add certain button to let user access the Internet directly. My cell phone is Sony Ericsson w580i. The advantages of this cell phone: (a) Dedicated key for MP3 function. The designers add an mp3 button on the phone, so user can play music when the slide is closed. (b) "Shake control". Without pressing any keys, user can just flick his wrist to control the MP3 function. This design may attract a lot of young people who like to listen to music (c) High resolution big screen. User will feel comfortable to use the cell phone to surf the web. There disadvantages of my cell phone: (a) the size of the keys is small. When I type the text message, sometimes I press the wrong key. The designer should increase the size of the keyboard. (b) When I use the phone, I cannot turn off lighting effects. The designer should consider that users may not want to use lighting effects. For example, in cinema, using lighting effects would disturb other people. (c) Battery life needs to be extended to support the extra entertainment function such MP3 player. If the battery life is not enough to make phone call, any extra function is useless. 2) Digital Television Receiver The most import work of digital television receivers is to receive and decode digital television
signals for output on TVs. From the users perspective, the designers should design an intuitive way for users to interact with the digital television receiver. The advantages of my digital television receiver: (a) I can watch high quality TV show. (b) I can add my favorite channels to a folder. So when open the digital television receiver, I can directly go to this folder and watch my favorite channels. (c) digital television receiver provide the function that users can see the TV schedule of each channel at anytime. So it is easy for users to select the TV program with the digital television receiver. Disadvantages of my digital television receiver: (a) There are too many remote controls such as the remote control for TV, DVD and remoter and digital television receiver. For example, I usually mistakenly use the remote control for TV to control the digital television receiver. (b) There are too many keys on the remote control. Some of them I never use (c) The digital television receiver can remind me with a pop-up notification. For example, my TV program is about to begin on the other channel and the digital television receiver will remind me to switch the channel. 3) PDA The main function of PDA is help user to manager information. The future development direction of PDA would be more intelligent than conventional touch screen. PDA can recognizes not only points and taps, but also shapes. The strengths of my PDA: (a) The size of the PDA is small and I can take it anywhere. (b) This PDA has a powerful translation function and I can use it to translate foreign language. (c) The PDA has some shortcuts such as time, transition, notebook. I can switch to any of these function by just pressing a key. The weakness of my PDA. (b) It is black and white display. (b) I cannot define the shortcut by myself. (c) The keys are too small. I have the press the keys very carefully. 2. Learning to listen to users 1) User A Interface: MacBook Tiger (a) No right mouse button Macs have no right mouse button. The user was not comfortable with this technology. He said, Maybe because I used to use Microsoft windows operating system. I feel the right mouse button can let the computer repose my intention immediately. As a new switcher, the user feels painful to learn the new commands and working style. (b) The notification for the low battery is not obvious. The user can barely notice its notification and the computer often shutdown suddenly without saving his current working data. (c) Video chat. Most of the user s friends are using MSN. When he used the MacBook, he cannot video chat with his friends via MSN. After he clicked "start webcam", the MSN
messenger will quit unexpectedly. 2) User B. Interface: Microsoft Windows Xp (a) Font too small to read. The user said, I am confused about setting font sizes. The font size appears fine on this application, but on some other application it difficult to read the font. (b) The IE is explorer is difficult to use and often collapse. (c) Searching speed is too low. When the user wants to search a file, it usually takes a long time and most of the situations is that the user cannot wait for the searching results and gives up the searching directly. 3) User C Interface: Microsoft Windows Vista (a) Annoying pop-up notification. The pop-up notifications in Vista is too many and often interrupt the user. I hate the User Account Control in Windows Vista, every time I try to run a program the notification will pop up the user said. Finally, the user finds a way to disable the User Account Control notification. (b) Software not compatible with vista. The user said, One of my favorite software-- Tencent QQ is not compatible with vista. (c) Aero interface reduces performance. He said, The interface look cool, but it make my computer become slow. In order to maintain good performance, I have to disable a lot of new features of the Vista interface. Discussion 1) Notification Ideally, the system should classify the notifications and utilize different techniques to deliver the notifications. The designer should know when and how to notify users. The import notification should be delivered immediately with a pop-up window. For instance, the notification for low battery is important to users. The system should pop up the notification window in front of the desktop and play a notification sound. For the low priority notifications, this type of notifications can be delivered periodically and not immediately. Otherwise it would be an interruption to users. These low priority notifications can be represented as balloons and user can ignore the notifications easily. 2) Compatibility issues The designs have to face the problem that the new system should be compatible with most current software. Furthermore, the interactive way with the system should be changed step by step, because it usually take a long time for users to accept a new way to interact with the system.
3. Power Law of Practice My program is designed for type test. In order to better analyze the user behavior, the program can to record the users type time and the number of type errors at each trials. In addition, the program only allow user to input lowercase. If the user types a capital letter, the program will pop-out the notification automatically. The interface of the program is shown in Figure 2. (a) (b) Figure 2. (a) The interface for the type test. The program only allow user to input lowercase. So if the user types a capital letter, there will be a pop-out notification. (b) Users can press the All Trail Results to see the results of all trails. (a) (b) Figure 3. The results of 30 trials. (a) The type time from the trial 1 to 30. At begin, the type time is decreased with trial numbers and then become stable. (b) The type errors from the trial 1 to 30. Power Law of Practice can be represented as the following equation:, (1) where is learning constant. According to equation (1), the learning constant can be computed as following: 2 (2) In this experiment, 30, 13.78, 6.13 s. So the learning constant 0.24.
Interesting Findings: 1) At first, the user kept his eyes focused on the keyboard. After the user repeated the trial several times, he switched his eyes focus from keyboard to screen. This means he believes that he has remembered the order of the keys and the type time is reduced at the same time. However, it does not mean the user will make fewer mistakes. The number of type errors the user made from the trial 15 to trial 30 is larger than the errors from the trial 1 to trial 15. 2) The subject is very relaxed when taking this test. Relaxation may be one of reasons to cause the user make some type mistakes. 3) The user often makes same mistakes. For example, the use typed the target letters as zyxwvutd three times. Obviously, the main reason is that the key d is next to s. Another reason is that it may be easy for people to make the same mistake. 4. Choice Reaction Time 1) According the Hick s Law:, where 12, the reaction time is 12 3.58. Let 0.15, 0.1, the reaction time approximately equal to 0.51 s. 2) (a) We can define, is the probability that target in the dynamic area and static area respectively. So the reaction time can be computer as following: 2 2 where n 4 n 8. So when the probability that the target is in the dynamic/static area is: 50/50, 75/25, and 90/10, the reaction time is a b, a b and a b. When a 0.15 s, b 0.1s, the reaction time is approximately 0.4 s, 0.375s and 0.36 s. (b) Minimum choice time for this dynamic menu is a2b (approximate 0.35 s) (c) Probability split 0/ 100 (dynamic/static) is maximum choice time, which is a3b (approximate 0.45 s) 3) Limitation of Hick s Law: (a) Relationship between reaction time and transmitted information is not linear. (b) The reaction time not only depends on the number of stimuli. For example, this law does not consider whether the user is familiar with the task. If the user gets training for a specific task, the reaction time will be definitely reduced. (c) In the real-world interface, the stimuli would be complex such as animation and buttons. Hick s Law is not appropriate to analyze these cases.