Speed is calculated as the reciprocal of reaction time, providing an alternative way to measure response efficiency. However, unlike reaction time, speed is more sensitive to extreme values, which can impact the overall average.
Formula for Speed
Speed = (1000 / Reaction Time) for each trial
Then, the sum of all speed values is divided by the total number of trials to get the average speed.
Example Calculation
1. Reaction times (ms):
500, 900, 300, 500, 1200, 300, 500, 345, 233, 984
2. Convert each reaction time to speed (1000 / Reaction Time):
• 1000 / 500 = 2.00
• 1000 / 900 = 1.11
• 1000 / 300 = 3.33
• 1000 / 500 = 2.00
• 1000 / 1200 = 0.83
• 1000 / 300 = 3.33
• 1000 / 500 = 2.00
• 1000 / 345 = 2.89
• 1000 / 233 = 4.29
• 1000 / 984 = 1.01
3. Sum of all speed values:
2.00 + 1.11 + 3.33 + 2.00 + 0.83 + 3.33 + 2.00 + 2.89 + 4.29 + 1.01 = 22.79
4. Divide by the number of trials (10):
22.79 / 10 = 2.27
Thus, the average reaction time is 576.2ms, and the corresponding average speed is 2.27.
Why Not Use 1000 / Average Reaction Time?
If we simply used 1000 / 576.2ms, we would get 1.73, which does not reflect individual variations in reaction times. Calculating speed for each trial first gives a different result because speed values are not linearly related to reaction time—slow responses have a greater effect on the final average.
While speed offers a different perspective, it is more sensitive to extreme values compared to raw reaction time.