Laboratory 25: Usability Testing

Summary: In this laboratory, we explore usability testing of a common household object.

Contents:

• Exercises
• Preliminaries
• A stopwatch in Scheme
• Usability mini-study
• Further mini-studies
• Questions for reflection

0. Preliminaries

b. We won't be programming today, but we will be using a Scheme procedure to time some of our activies. So, start DrScheme.

1. A stopwatch in Scheme

a. Copy the definition of elapsed-milliseconds below and paste it into the definitions pane of DrScheme.

;;; Procedure:
;;;   elapsed-milliseconds
;;; Purpose:
;;;   Measures the elapsed time of some human activity, in simulation of a stopwatch.
;;; Parameters:
;;;   None
;;; Produces:
;;;   t, an integer
;;; Preconditions:
;;;   None
;;; Postconditions:
;;;   t is the time elapsed between the commencement of the procedure call and the time
;;;     the user presses the Enter key, to the nearest millisecond.
;;; Pragmatics:
;;;   Note that human reaction time is about 1/10th of a second, or 100 milliseconds.
(define elapsed-milliseconds
  (lambda ()
    (let ((initial-ms (current-milliseconds)))
      (display "Timer started. Press ENTER to stop.")
      (read-line)
      (let ((final-ms (current-milliseconds)))
        (- final-ms initial-ms)))))

b. Run (elapsed-milliseconds) a few times (perhaps counting 1-Mississippi, 2-Mississippi, etc.) to verify that it gives reasonable measurements. Remember that there are 1000 milliseconds per second.

c. Use Esc-P to recall the previous command, but don't hit Enter to run the command just yet. When you are ready, hit Enter twice as fast as you can. Do this several times to verify that human reaction time is around 100-200 milliseconds.

2. Usability mini-study

As a part of this lab your group will be conducting several mini-studies. 

Choose one group member to be the participant for the first mini-study, and another to be the facilitator.  The remaining one or two group members will be observers.  My goal is that each of you experience playing each role and that in the process you learn something about different aspects of usability in practice.

Here are the instructions for the facilitator.  (We'll also hand out paper copies.)

Here is a form for the observer.

The participant should smile, relax, and follow along with the facilitator, whose job it is to guide you through the study.

3. Further mini-studies

You might have noticed that there are more devices than groups.  When you are done with your first mini-study, assign everybody a new role and raise your hands.  We'll come to collect the observer's notes and give your team a new device for the next mini-study.

Let me know when everyone in your group has experienced each role.

4. Questions for reflection

We'll try to take the last 5-10 minutes to reflect on our experiences.  Here are some questions to think about.

1. In what different contexts do people use alarm clocks? Are different aspects of usability important in those contexts?

2. Have you encountered usability problems in your own everyday use of alarm clocks?

3. Which clock did you find the most usable? Least usable? Why?

4. Which clock do you think was the most expensive?  Least expensive? Why?

5. What was the most difficult aspect of playing each role? The most rewarding aspect?

6. Should I use this exercise again?

Janet Davis (davisjan@cs.grinnell.edu)