Fitt's Law

Question 1

What is Fitt’s law

Answer 1

Mathematical model that predicts that the average movement time to hit a target along a one-dimensional path is proportional to the width of the target and the distance of the target

Question 2

What is the amplitude?

Answer 2

Distance between targets

Question 3

What is the avg movement time?

Answer 3

Function of index of difficulty.

Question 4

What’s the index of difficulty?

Answer 4

The index of difficulty is a measure in bits of how difficult it is to hit a target of width W from distance D.

Maximise W and minimise D

Question 5

What does Fitts’ law enable us to measure?

Answer 5

Throughput

Question 6

What does throughput measure?

Answer 6

Number of bits of information a user can communicate per second independently of a specific target.

Question 7

What are the assumptions of Fitt’s law

Answer 7

• Closed loop interaction
• Biologically plausible interval
• Regression coefficients a and b vary depending on the task.
• Different pointing devices can be compared by their throughput.

Question 8

What are the limitations of performance models?

Answer 8

Currently only low-level actions are modelled reliably

Question 9

What are the other limitations of Fitts’ law?

Answer 9

Only works on a one dimensional plane, which is an issue as users usually move interaction devices in more than one plane.