"Cramming" Is a Technique Often Used by Students to Prepare

Multiple Choice

"Cramming" is a technique often used by students to prepare for exams,in which they study for extended hours only a few days before the exams.Often students drink caffeinated beverages to help them stay awake while cramming for exams.Five students were randomly selected and asked to drink highly caffeinated beverages before their first midterm exam and then drink only water before their second midterm exam in the same subject.The difference of the scores (midterm 2 - midterm 1) is shown below for the five students. What is the mean of the Wilcoxon signed rank test statistic,W⁺,under the null hypothesis that there is no difference?

A) 3
B) 12
C) 15
D) None of the above