An investigator would like to examine the association between depression and stress scores among individuals with a history of psychiatric treatment. He notes that in this particular group of individuals, the depression scores were highly left skewed. That is, the majority of subjects clustered at the high end of the scale, but there were a few that had very low scores. Stress scores for this subset were normally distributed. What test should he use? Question 20 options: Paired t-test Wilcoxon signed-rank test Spearman correlation Pearson correlation