Name: _____________________________
Please complete the following problems using SPSS (and Excel for graphs). Interpret all results at the .05 significance level and round to two decimal places. Record your responses in the spaces provided and make sure you do not miss any questions. Make sure to include statistical notation when appropriate and double-check your data entry!
1. A researcher wants to evaluate the learning ability of college students with various background sounds during learning. She randomly divides 21 participants into three groups. All students study a passage of text for 30 minutes. Those in group 1 study with background sound at a constant volume in the background. Those in group 2 study with background sound that changes volume randomly. Those in group 3 study with no sound at all. After studying, all students take a 10-point multiple choice test about the material. Their scores follow:
Constant sound Random sound No sound
7 5 5
4 5 6
6 3 7
8 4 9
6 4 8
6 6 7
9 2 6
A. What statistical test should you perform? Be as specific as possible. (7 points)
B. What is the overall result of the statistical analysis (hint: think “first sentence”)? Include statistical notation. (9 points)
C. Is the constant sound group significantly different from the random sound group? Describe the relationship and include statistical notation. (9 points)
D. Is the constant sound group significantly different from the no sound group? Describe the relationship and include statistical notation. (9 points)
E. Is the random sound group significantly different from the no sound group? Describe the relationship and include statistical notation. (9 points)
F. Write a sentence in “plain English” that describes the results of the experiment. (7 points)
Bonus: Graph your results (include axis titles, chart title, and SEM error bars). (3 points)
2. In order to better prepare for her 8:00am classes, a statistics graduate student designs an experiment to see how various strategies improve test scores. Getting extra sleep and drinking coffee are often said to be good ways to improve focus in class. She assigns half of her participants to 4 hours of sleep the night before a test and the other half to 8 hours. Within these groups, half of the participants are given 50mg of caffeine the morning of the test and the other half are given 100mg of caffeine. She then measures exam performance on a test with scores ranging from 1-15. (50 points)
4 hours of sleep 8 hours of sleep
50mg of caffeine 10
7
9
7
10
8
9 14
12
15
11
12
10
12
100mg of caffeine 13
10
11
9
15
11
10 11
13
9
14
12
10
13
A. What test should you perform? Be as specific as possible. (5 points)
B. Write a sentence describing the main effect of caffeine (include statistical notation). If the main effect was significant, write a second sentence describing which group scored higher/lower. (15 points)
C. Write a sentence describing the main effect of sleep (include statistical notation). If the main effect was significant, write a second sentence describing which group scored higher/lower. (15 points)
D. Write a sentence describing if there was a significant interaction effect or not (include statistical notation). Note: you do not need to describe the different groups here. (15 points)
Bonus: What do these results suggest? Is there an ideal sleep/caffeine combination that appears to be the most effective or particularly ineffective? (3 bonus points)
Bonus: Graph these results (include axis titles and chart title) (3 bonus points)