Test of Two Variances · Exercise 23

Thirty men in college were taught a method of finger tapping. They were randomly assigned to three groups of 10, with each receiving one of three doses of caffeine: 0 mg, 100 mg, or 200 mg. This is approximately the amount in zero, one, or two cups of coffee. Two hours after ingesting the caffeine, the men had the rate of finger tapping per minute recorded. The experiment was double blind, so neither the recorders nor the students knew which group they were in. Does caffeine affect the rate of tapping, and if so how?
Here are the data:

$$\begin{array}{cccccc}\text{0 mg}& \text{100 mg}& \text{200 mg}& \text{0 mg}& \text{100 mg}& \text{200 mg}\\ \text{242}& \text{248}& \text{246}& \text{245}& \text{246}& \text{248}\\ \text{244}& \text{245}& \text{250}& \text{248}& \text{247}& \text{252}\\ \text{247}& \text{248}& \text{248}& \text{248}& \text{250}& \text{250}\\ \text{242}& \text{247}& \text{246}& \text{244}& \text{246}& \text{248}\\ \text{246}& \text{243}& \text{245}& \text{242}& \text{244}& \text{250}\end{array}$$

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Statistics · §13.4 Test of Two Variances · Exercise 23