Question

A school psychologist notes that the average number of times that students are disruptive during class is 1.4 (µ = 1.4) times per day. Following recent classroom policy changes, the psychologist tests if the number of disruptions during class has changed. He records the following number of disruptions observed during a class day: 2, 4, 3, 5, 4, 1, 1, and 4.

a) Test the hypothesis that the number of complaints has increased or decreased using a .05 level of significance. State the value for the test statistic and the decision to retain or reject the null hypothesis.
b) Compute effect size using estimated Cohen’s d.

Answer 1

Explanation:

a)The null hypothesis states that the average number of disruptions during class is still 1.4 times per day. The alternative hypothesis states that the average number of disruptions during class has changed. We calculated the t-value to be 1.97 and compared it to the critical value of 2.36. Since the t-value is less than the critical value, we fail to reject the null hypothesis. This means there is not enough evidence to conclude that the number of disruptions during class has changed.

b) The effect size, computed using Cohen's d, is approximately 0.838. This indicates a medium effect size, suggesting a noticeable difference in the number of disruptions during class before and after the policy changes.