Question

A researcher would like to determine whether an over-the-counter cold medication has an effect on mental alertness. A sample of n = 25 participants is obtained, and each person is given a standard dose of the medication one hour before being tested in a driving simulation task. For the general population, scores on the simulation task are normally distributed with μ = 58 and σ = 20. The individuals in the sample had an average score of M = 56.

Compute Cohen’s d to measure the size of the effect.

Answer 1

The Cohen's d value is -0.1. From this value, we can conclude that the effect size is very small.