A cheerleading squad received a mean rating (out of 100 possible points) of 75 ± 12 (μ ± σ) in competitions over the previous three seasons. The same cheerleading squad performed in 36 local competitions this season with a mean rating equal to 78 in competitions. Suppose we conduct a one-sample z test to determine whether mean ratings increased this season (compared to the previous three seasons) at a .05 level of significance.

(a) State the value of the test statistic and whether to retain or reject the null hypothesis.

(b) Compute effect size using Cohen's d and state whether it is small, medium, or large.