| Fitts' Law Calculator for Young and Old (Approximation) | |||||
| Movement time for a limb is a function of the difficulty of the movement, the Index of Difficulty (ID), which depends on the amplitude of the movement, how far away the target is, together with how small it is, its width | |||||
| Distance (A) | Width (W) | ||||
| Enter Distance from the starting position of the limb to the Center of Target (Amplitude) and the width (W) of the Target in the same units of measurement (cm, inches, etc.) | |||||
| Estimates are the movement time to the target in milliseconds based on different Fitts' Law formulas, assuming a y-intercept = 0, and ages of 25 for young and 65 for older Adults | Young Time (ms) | Old Time (ms) | |||
| Welford | 309 | 540 | |||
| Fitts | 400 | 700 | |||
| Shannon | 317 | 555 | |||
| Model Human Processor (MHP) (Card Moran & Newell 1983) calculations assume that there is incremental time,70ms for a motor processor cycle | |||||
| Jastrzembski thesis (2006) estimates 146 ms for older Old motor processor cycle time | |||||
| MHP Welford | 379 | 686 | |||
| MHP Fitts | 470 | 846 | |||
| MHP Shannon | 387 | 701 | |||
| Movement Time = a+b*ID with non-zero intercept; or MT=b*ID with line through the origin | |||||
| Slope values for b are based on Jastrzembski (2006) thesis: 100 for young Adults and 175 for older Adults | |||||
| Formulas for Fitts' Law taken from MacKenzie, I. S. (1995). Movement time prediction in human-computer interfaces. In R. M. Baecker, W. A. S. Buxton, J. Grudin, & S.Greenberg (Eds.), Readings in human-computer interaction (2nd ed.) (pp. 483-493). Los Altos, CA: Kaufmann. | |||||
| Fitts' ID | log2(2A/W) | ||||
| Welford's ID | log2(A/W + 0.5) | ||||
| Shannon's ID | log2(A/W+1) | ||||