# Module 322. Exercise 3 in Module 20 examined whether adding

Module 322. Exercise 3 in Module 20 examined whether adding a fragrance to a window cleaner led people to believe that it cleans better than an unscented product. There were 12 subjects in each group: scented or unscented. The mean cleaning effectiveness rating for the group getting the scented cleaner was 7.42. The mean cleaning effectiveness rating for the group getting the unscented cleaner was 6.00. The standard deviation for cleaning effectiveness ratings across all subjects is 1.369. A t test showed that the scented cleaner was rated as a significantly more effective cleaner (t = 2.84, α < .01).a. Calculate the effect size for this study, using both Cohen’s d and effect size rb. Interpret the result: Was there a practical difference in cleaning effectiveness between scented and unscented cleaners?Module 338. You are designing a study to be evaluated with a two-sample nondirectional independent t test at α. = .05. You want .90 power. You expect Cohen’s d to be about .40. How many subjects will you need per group?14. You are designing a three-group study to be evaluated with a one-way ANOVA at α = .05. You expect effect size η to be about .29. How many subjects will you need per group for .80 power?