A researcher is interested in studying changes in marital satisfaction over the course of marriage. She hypothesizes that marital satisfaction is highest when couples are newly married, that it decreases during the middle years of marriage, but rises again during later years of marriage. In order to test her hypothesis, she recruits fifty married couples within each of the following conditions: (1) married less than 10 years; (2) married 15-20 years; (3) married more than 25 years. All 150 couples (50 from each condition) complete a standardized measure of marital satisfaction.
If the experimenter had reason to believe that the data would be better analyzed by a nonparametric test, which would be the most appropriate test?
A) Wilcoxon's signed-ranks matched-pairs test
B) The Mann-Whitney test
C) Kruskal-Wallis test
D) The Friedman test.

Question

Quizplus · Accepted Answer

The Kruskal-Wallis test is a nonparametric test used to compare three or more groups. In this case, the researcher is comparing three groups (married less than 10 years, married 15-20 years, and married more than 25 years) on a measure of marital satisfaction. This test does not assume normality, which is useful if the data do not meet the assumptions of parametric tests. The Wilcoxon signed-ranks test and the Mann-Whitney test are both nonparametric tests, but they are used to compare two groups, not more than two groups as in this case. The Friedman test is used to analyze repeated measures data, which is not the case in this study.

A Researcher Is Interested in Studying Changes in Marital Satisfaction