Researcher is investigating effectiveness of new study-skills training program for elementary school children. A sample of n= 25 third grade children and each child is given standardized achievement test at end of year. For regular population of third grade children, scores on test form normal distribution with mean of µ = 150 and standard deviation of σ = 25. Mean for sample is M = 158.

a. Draw the suitable distribution, and locate critical regions for α = .05.
b. Compute test statistics (z score) for the sample.
c. What decision must be made about effect of program?
1. To test effectiveness of a treatment, sample of n = 25 people is selected from normal population with mean of µ = 60. After treatment is administered to individuals in sample, sample mean is found to be M = 55.

a. Calculate Cohen's d measure effect size for both tests (σ = 20 and σ = 10).
b. Explain how sample size affect outcome of hypothesis test. How does sample size influence measures of effect size.