A common situation faced by researchers working with special populations, such as neurologically impaired people or people with less common psychiatric conditions, is that the studies often have small sample sizes due to the relatively few numbers of patients. As a result, these researchers often turn to nonparametric statistical tests. For each of the following research descriptions, state which nonparametric hypothesis test is most appropriate: Spearman rank-order correla - tion coefficient, Wilcoxon signed-rank test, Mann- Whitney U test, or Kruskal-Wallis H test. Explain your answers.
a. People who have had a stroke often have whole or partial paralysis on the side of their body opposite the side of the brain damage. Leung, Ng, and Fong (2009) were interested in the effects of a treatment program for constrained movement on the recovery from paralysis. They compared the arm-movement ability of eight stroke patients before and after the treatment.
b. Leung and colleagues (2009) were also interested in whether the amount of improvement after the therapy was related to the number of months that had passed since the patient experienced the stroke.
c. Five of Leung and colleagues' (2009) patients were male and three were female. We could ask whether post-treatment movement performance was different between men and women.