Human Factors 2004 Final paper Group member: Polo Chau. My IKEA alarm clock

Transcription

1 Human Factors 2004 Final paper Group member: Polo Chau My IKEA alarm clock Introduction In this report, we are going to talk about the Human Factors problems about the IKEA alarm clock. We will show you how the problems come up in two typical tasks in using the clock, and how they make it more difficult to use. Then, we will suggest design changes to solve the problems and discuss their tradeoffs. Below are the front, back and side views of the alarm clock. The alarm clock has a 9cm diameter. Its frame is made of steel. On its back, there are 2 knobs. The knob on the right is for adjusting the time while the one on the left is for adjusting the alarm. There is a small level area at its bottom so it can rest on a flat surface. The clock was discontinued about 2 years ago, so it is no longer available from IKEA. In the following section, we will talk about the task analyses that we have performed on 2 typical tasks in using the clock. Task analysis is useful in providing a detailed description about what people need to do and consider while executing a task.

2 Task analysis We have chosen 2 common tasks that an alarm clock owner would normally do every day. The 2 tasks are (1) Tell the time in bed, and (2) Set alarm to 8 o clock. We have performed a task analysis on each of them. For each of the analyses, we will list the task s correct sequence of actions, the decisions and responses required, and the modalities used when performing the task. Recognizing these elements is important because we can estimate the severity of the Human Factor problems that we will talk about in a later section by noting which parts of the tasks are affected. Besides, when we suggest solutions of the problems, we will have a better idea about which parts of the tasks will be improved. Task 1: Tell the time while in bed Correct sequence of actions: 1. Open eyes 2. Scan for clock surface 3. Determine current hour 3.1. look at the 2 clock arms 3.2. decide which one is shorter, and identify it as hour arm 3.3. look for the hour marking closest to hour arm 3.4. mentally rotate clock surface 90 degree anti-clockwise 3.5. identify approximate hour 3.6. remember hour in WM 4. Determine current minute 4.1. look at the other arm (the longer arm) 4.2. look for minute marking closest to the minute arm 4.3. mentally rotate clock 90 degree anti-clockwise 4.4. identify approximate minute 4.5. remember minute in WM 5. Combine hour and minute in WM to determine current time

3 Decisions required: 1. Which arm is shorter? 2. The hour arm is closest to which hour marking? 3. The minute arm is closest to which minute marking? Responses required: 1. Mentally rotate clock anti-clockwise (respond to the fact that clock is rotated) 2. Remember hour and minute in WM (respond to the time just retrieved) Modalities used: 1. Scan for clock surface: visual 2. Look at hour and minute arms: visual 3. Look for closest markings to the arms: visual Task 2: Set alarm to 8 o clock Correct sequence of actions: Lift clock Look at alarm arm Turn knob clockwise Desired alarm time? Yes End No Yes Hand on alarm knob? No Turn to back of clock Turn to front of clock Visually search for alarm knob Put one hand on alarm knob

4 Decisions required: 1. Does the current alarm time match the desired alarm time? 2. Is my hand already on the alarm knob? 3. Which knob is for adjusting the alarm arm? 4. Should I turn the alarm knob clockwise or anti-clockwise? Responses required: 1. Turn knob to reduce the difference between current alarm time and the desired one. 2. Turn clock to the back (respond to situation that user needs to find the knob) Modalities used: 1. Lift clock: tactile 2. Look at alarm arm to determine current alarm time: visual 3. Turn clock to the back and to the front: tactile 4. Turn knob to adjust alarm time: tactile We conducted a user study at an earlier time, during which we asked 2 users to perform the tasks. In the following section, we will describe the characteristics of the users and the setting in which they perform the tasks. And then in a later section, we will discuss the Human Factor issues that we identified from the user study. User study In the user study, we asked 2 persons to use the alarm clock to perform the 2 tasks. Below are their characteristics: User 1 User 2 Gender Female Male Age Mid-20s Early-20s Sight Normal Shortsighted glasses Experience Have used mechanical alarm clock before Environment Dimly-lit room

5 Both of the users had used a mechanical alarm clock before, so they knew they could adjust the alarm using a alarm knob on the back of the clock. The were invited to perform the task in a dimly-lit room, which closely matched the lighting condition where an alarm clock is usually used. The tasks that we asked them to perform were (1) Tell the time while in bed, and (2) Set the alarm to 8 o clock. We noted that it would not be suitable to ask them to perform the first task in bed; therefore we asked them to go into a sleeping position instead. Task 1: Tell the time while in sleeping position Setting: Before the task began, we asked the users to lay their heads on the table and close their eyes. User 1 was asked to take off his glasses. They were about 2 feet from the alarm clock. This setting simulated the situation where a person is in bed with the alarm clock on a bed-side table. The image on the right illustrates this setting Task 2: Set alarm to 8 o clock Setting: First, we changed the alarm time to 11 o'clock. Then we put the clock on the table. The users sat in front of the clock, facing it. Then they started with the task. In the following section, we will talk about the Human Factor issues that we have identified from the user study.

6 HF issues identified from user study During the user study, we observed how the users perform the tasks, and noted down the problems that affected their performances. The problems are listed in the following table. Step Problem Problem Type Explanation Task 1: Decide which arm is shorter Delay in deciding Visual sensing Arms difficult to distinguish have same thickness, and about the same length (3) Task 1: Mentally rotate clock 90 degree anti-clockwise Delay in deciphering the time Cognition Users were confused by the same markings used for each hour the clock surface was rotated, but it looked the same as it hadn t. (3) (4) Task 2: Locate alarm knob Delay in finding alarm knob Visual sensing Knob labels are raised printing on black background hard to read with low contrast (1) Task 2: Locate alarm knob Delay in finding alarm knob Visual sensing Knobs look the same hard to discriminate. Identification of the knob relies solely on the difficultto-read knob labels (mentioned in the previous problem) (2) (3) Task 2: Turn alarm knob Knob difficult to grip and turn; leaves imprints on fingers Tactile Knob is tiny (1) Task 2: Turn alarm knob Twist wrist too much Tactile Knobs have inappropriately high Control / Response ratio requires many turns to make slight adjustment (5)

7 From the table, we can see that the problems are mainly about visual sensing and tactile response. (The cognition problem is largely caused by the visual ambiguity of the time markings.) More specifically, the clock has unclear labels for its time markings and adjustment knobs. The knobs are too tiny to grip, and requires too many turns to make slight adjustment to the time. In the following section, we are going to suggest some design changes to overcome these problems. Redesign and its justification We have made changes to the front and the back of the alarm clock. Front We have made the hour arm shorter and thicker than the original, so that it looks distinctly different from the minute arm. This design change may slightly increase the production costs; we think, in the original design, the hour arm is only a cut-short version of the minute arm, while in our new design the hour and minute arms need to be manufactured separately.

8 We have added 4 major numeric time markings to the clock surface 3, 6, 9, 12 so that people can tell the time with little mental effort. It is unlike the original design where people need to find out which stroke corresponds to which hour; it is a substantial mental workload for people especially when they are in bed, only half awake, looking at the clock on their bed-side table. Adding the numerical markings may be less aesthetically pleasing, but we feel it is a necessary change because it allows the time to be very easily recognized. Back We have made both the time and alarm knobs bigger, where the alarm knob is about twice as big as the time knob. Also, they have different shapes: alarm knob is circular and time knob is hexagonal. They have bright and contrasting color so they are even more distinguishable (2) and can be easily seen even under dim light. We have made the alarm knob bigger because we think that it is used nearly every day, much more often than the time knob which may be used only once or twice when the clock is newly bought, or when the clock battery is replaced. The alarm knob s bigger size will make it look more prominent and easy for people to grip. People do not even have to turn

9 the clock to the back to locate the alarm knob; they can just search for the knob through touching. To improve the legibility of the knob labels, we have made them bigger and painted them with the same colors as their corresponding knobs. We believe using different colors, sizes and shapes for the knobs may increase the production costs slightly. We have decreased the Control / Response (C/R) ratio for the knobs so that the time can be adjusted with fewer turns. However, this may need to change the internal gear ratios of clock. Conclusion In our process of redesigning the IKEA alarm clock, we used task analyses to find out the correct steps in performing 2 common tasks with the clock. Then in our user studies, we invited 2 users to use the clock and observed and noted down the problems they had when using it. Afterwards, we listed the problems that we recorded, and suggested design changes to overcome them. In our redesign, we have not compromised any existing functions of the clock. Our changes to its appearance are kept to a minimum. Our redesign focuses on resolving ambiguity of elements on the clock surface and the knob labels, as well as making the adjustment knobs easier to use. We have: made the hour arm shorter and thicker arms more distinguishable added numerical hour markings easier to tell the time used different colors, sizes, and shapes to for the 2 knobs knobs more distinguishable used bigger knobs and lowered their C/R ratio knobs easier to turn

10 Besides, we have added one extra feature that would further make the clock easier to use: we have made the more-frequently-used alarm knob bigger, so people can very easily locate the knob through touching without having to turn the clock around. (5) In short, we feel that our new design is successful and is a significant improvement over the existing design. We believe people will find our new alarm clock very pleasant to use. References (1) Principle 1. Make displays legible Wickens book P.186 (2) Principle 4. Redundancy gain Wickens book P.188 (3) Principle 5. Discriminability Wickens book P.188 (4) Principle 11. Replace memory with visual information Wickens book P.191 (5) Keep control movement short Lecture 15 P.18