Practice Exercise: T Test for Dependent Means
Use the Paired Samples T Test function in SPSS to answer each of the following questions. (Assume a nondirectional research hypothesis and critical level of significance of .05)
Researchers interested in the effects of stress on beta-endorphin levels in the blood took beta endorphin level measures from 19 patients 12 hours before surgery and again 10 minutes before surgery. The data are presented below:
|
12 Hours Before
|
10 Minutes Before
|
|
13.00
|
6.50
|
|
9.50
|
14.00
|
|
8.00
|
10.50
|
|
15.00
|
14.00
|
|
8.00
|
14.50
|
|
14.50
|
30.00
|
|
8.00
|
18.00
|
|
6.50
|
18.50
|
|
10.50
|
6.50
|
|
8.50
|
6.00
|
|
13.50
|
25.00
|
|
11.00
|
12.00
|
|
10.00
|
24.00
|
|
20.00
|
42.00
|
|
14.80
|
19.00
|
|
20.00
|
36.00
|
|
18.50
|
10.50
|
|
7.40
|
2.50
|
|
5.00
|
2.00
|
1. Write an appropriate null hypothesis for this analysis.
2. What are the mean beta-endorphin levels of patients 12 hours before surgery and 10 minutes before surgery?
3. What are the standard deviations of the beta-endorphin levels 12 hours before surgery and 10 minutes before surgery?
4. What is the observed or computed value of t?
5. What is the value of the degrees of freedom that is reported in the output?
6. Based on the results of the T Test for Dependent Means, what would you conclude about the effects of stress on the level of beta-endorphins in the blood?
7. Write a statement as it might appear in an article that reports the results of the T Test for Dependent Means.