Does speed in completing a test correlate with one's grade? Here are test scores for eight students in one of our statistics classes. They are arranged in order from the student who turned in the test first to the student who turned in the test last.
98 74 87 92 88 93 62 67
a. What are the two variables of interest? For each variable, state whether it's scale or ordinal.
b. Calculate the Spearman correlation coefficient for these two variables. Remember to convert any scale variables to ranks.
c. What does the coefficient tell us about the relation between these two variables?
d. Why couldn't we calculate a Pearson correlation coefficient for these data?