Exercise 3 - Mensch-Maschine-Interaktion 1 (MMI 1)
Wintersemester 2008/09
Exercise 3 - MMI 1
Topic: Law of Steering
5. Reading
a) Read the paper Beyond Fitts' law: models for trajectory-based HCI tasks by Accot and Zhai (1997) and write a short summary (100-200 words).
b) Can you find a tunnel shape where the Law of Steering certainly won't work?
6. Law of Steering (2/2)
The Law of Steering predicts how long
it takes a user to navigate a pointer through a tunnel. For a straight
tunnel with length A and constant width W, the average time to pass ist
is a + b * A/W. The term A/W is called index of difficulty (ID).
Verify the validity of the law with a small study and find out a and b
for the different movement directions (you should have a working test
application by now):
- Find 4 participants.
- Each participant has to do two rounds, each consisting of
the 64 trials. There should be a small break between rounds. The first
round is just for training.
- If the participant touches a tunnel wall or leaves the
start area in the wrong direction this is counted as an error. You can
let the participant complete the trial nevertheless in order to not
frustrate him.
- Log all data.
Afterwards, analyze the data:
- Throw away the data from the training round.
- Group the trial data by tunnel direction. Further analyze
every direction seperately.
- Clean the data of tasks where an error was made. Note
the error rate (errors/trials) for every combination of width/length of
the tunnel.
- For every combination of width/length of the tunnel
calculate the average completion time of all participants.
- Calculate the ID for every combination.
- Plot all data points of the direction group in a
scatterplot. The x axis is the ID, the y axis is the completion time.
- Fit a linear function a+b*x through the data points and
document a and b.
- Is there a difference between the direction groups?
Thoroughly document the experiment and the analysis. Include a screenshot and all
graphs. Submit the raw data in separate files.
Submission
Submit your solution via UniWorx.
Unless otherwise specified, all files have to be either Adobe PDF or
UTF-8 plain text. All other files will be automatically deleted.
Please put all files concerning one sub-task of this assignment into a sub-folder inside the
ZIP file.
Schema/Example:
./
5/
a/
summary.txt
b/
further_questions.txt
6/
report.pdf
raw_data_00.csv
raw_data_01.csv
Do not use any other directory layout.
Deadline:
Monday, 03.11.2008,
09:00 (UTC+2)