A professor has a teaching assistant record the amount of time (in minutes) that

Question

A professor has a teaching assistant record the amount of time (in minutes) that a sample 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.

Use the normal approximation for the Mann-Whitney U test to analyze the data above. (Round your answer to two decimal places.)
z =

With Microsoft
PowerPoint Without
Microsoft
PowerPoint 23 21 6 19 14 10 11 15 5 18 4 12 8 9 13 7

Explanation / Answer

Solution:-

Mann-Whitney Test and CI: With Powerpoint, Without Powerpoint

N Median
With Powerpoint 8 9.50
Without Powerpoint 8 13.50

Point estimate for 1 - 2 is - 4.00
95.9 Percent CI for 1 - 2 is (-10.00,4.00)
W = 56.0
Test of 1 = 2 vs 1 2 is significant at 0.2271

Normal approximation for the Mann-Whitney

Sample 1
Sum of ranks: 56
Mean of ranks: 7
Expected sum of ranks: 68
Expected mean of ranks: 8.5
U-value: 44
Expected U-value: 32

Sample 2
Sum of ranks: 80
Mean of ranks: 10
Expected sum of ranks: 68
Expected mean of ranks: 8.5
U-value: 20
Expected U-value: 32

Sample 1 & 2 Combined
Sum of ranks: 136
Mean of ranks: 8.5
Standard Deviation: 9.5219

The U-value is 20.
The critical value of U at p < 0.05 is 13.
Therefore, the result is not significant at p < 0.05.
The Z-Score is -1.20774.
The p-value is .22628.
The result is not significant at p < .05.

Sample 1 Sample 1 Ranks Sample 2 Sample 2 Ranks 4 1 7 4 5 2 9 6 6 3 10 7 8 5 12 9 11 8 15 12 13 10 18 13 14 11 19 14 23 16 21 15

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