A Researcher Decided to Conduct an Experiment to Study the Effect

A researcher decided to conduct an experiment to study the effect of caffeine by randomly dividing nine people into two groups. Group 1, consisting of five study subjects had a cup of coffee to start the experiment. Group 2, consisting of four people, had decaffeinated coffee. The study subjects did not know which group they belonged to. All study subjects were then asked to tap their finger. The measurement taken was the number of finger taps per minute. This type of data is often skewed and the researchers decided that they should not use a two-sample t test. They chose a Wilcoxon rank sum test and recorded the ranks of the subjects in the caffeine group. The standard deviation of this test statistic is given by:

A) 16.67.
B) 4.083.
C) 22.5.
D) None of the answer options is correct.