A professor had a teaching assistant record the amount of time (in minutes) that a total of 16 students engaged in an active discussion. The assistant observed 8 students in a class who used a slide show presentation and 8 students in a class who did not use a slide show presentation. Based on the results shown in the table, test whether active discussion times differed using the Mann-Whitney U test at a .05 level of significance. State whether to retain or reject the null hypothesis.
With Slide Show ___________________________ Without Slide Show
__Presentation________________________________ Presentation___
7..............................................................23
14............................................................11
12............................................................15
8..............................................................18
10............................................................21
13............................................................. 5
6.............................................................. 4
9..............................................................19