2. Overview
• What is 'ʹFi#s Law'ʹ?
• Research Design
• Research Method
• Data Collection
• Results
• Analysis
• Discussion
3. What is 'Fitts’ Law'?
An empirical model explaining speed-‐‑accuracy tradeoff
characteristics of human muscle movement
• As a target gets smaller and/or further away, it takes
longer to move to it
http://www.interaction-design.org/encyclopedia/fitts_law.html)
4. Research Design
• Independent Variables
-‐‑ size of the target
-‐‑ distance of the target from start bu#on
• Dependent Variable
-‐‑ time to move to the target
• Within participants design
• Three test conditions
5. Research Method
• Testing application developed in HTML and
javascript
• 1st version
-‐‑ bu#ons randomly assigned
• 2nd version
- buttons manually assigned
- previously saved positions and sizes in arrays
• Size = [5, 10 , 15 , 20 , 25];
index = [0, 3 , 2 , 1 , 4];
output = [5, 20, 15, 10, 25];
6. Research Method
• Three cases of testing:
o Same distance from start bu#on, varying target size.
6 trials for each participant
o Same size target, but varying distance from start
bu#on.
10 trials for each participant
o Varying target size and distance from the start
bu#on
10 trials for each participant
7. Experiment description
• Same computer, same mouse
• In same order:
• Conducted in the same environment
Varied size Varied bothVaried distance
15. Error
• Error = Actual Time -‐‑ Estimated Time
• Actual Time: the real time spent by users in clicking a
bu#on
• Estimated Time: the time that should be used according
to fi#s law
19. Correlation and Dependence
Pearson product-‐‑moment correlation coefficient is a
measure of the correlation (linear dependence) between
two variables X and Y.
The coefficient ranges from -‐‑1 to +1
The sample correlation coefficient is wri#en:
21. Discussions
We cannot say that we have accurately replicated
Fi#s’ law :
• Unequal no. of trials across the conditions
• different motor skills
• experience with mouse vs trackpad
