This question is about Fitts' Law - Speed Accuracy Trade-off

The chart below shows the results of how changing the difficulty of the movement (and therefore the accuracy requirements) affects the speed of movement (as determined by the movement time).

My question: Compare the predicted MTs in 2) to your actual MTs for the conditions with an ID of 3 and an ID of 4. How close are the predicted values to your actual values? Explain any potential reasons why there might be a discrepancy.

Here are some formulas : ID = log2(2A/W), MT = a + b(ID), MT = a + b[log2(2A/W)]

Here is the formula for the chart below: MT = 76.061 +105.91_ [log2(2A/W)]

G Movement Amplitude (A) Target Width (W) Index of Difficulty (ID) Movement Time (MT) 215 IN 239 291 354 Co CO + IN 426 520 Fitt's Law 600 y = 105.91x + 76.061 520 R2 = 0.9044 500 426 400 354 Movement Time (Msec) 291 BOO 239 215 200 100 33 34 35 36 37 0.5 15 2.5 B.5 45 38 39 40 Index of difficulty (bits)