You interview 75 students in their freshmen year and again in their senior year. Each interview includes information about height and weight, allowing the computation of each student's body mass index, BMI. You wish to assess whether there has been a significant change from freshmen to senior year in their BMIs. Select the best method to use to assess whether there has been a significant change from freshmen to senior year in their BMIs.

Select the best method to use to assess whether there has been a significant change from freshmen to senior year in their BMIS.

a. two-way ANOVA test
b. Wilcoxon rank sum test
c. Kruskal-Wallis test
d. Wilcoxon signed rank test