1.Use these data to answer question 1a and 1b. These are saved as Chapter 5 Date Set.
| Correct |
Attitude |
| 17 |
94 |
| 13 |
73 |
| 12 |
59 |
| 15 |
80 |
| 16 |
93 |
| 14 |
85 |
| 16 |
66 |
| 16 |
79 |
| 18 |
77 |
| 19 |
91 |
a. Compute the Pearson product-moment correlation coefficient by hand and show all and show all your work.
b. Construct a scatterplot for these 10 values by hand. Based on the scatterplot, would you predict the correlation to be direct or indirect? Why?
4. Use SPSS to determine the correlation between hours of studying and grade point average in these honor students. Why is the correlation so low?
| Hours of studying |
GPA |
| 23 |
3.95 |
| 12 |
3.9 |
| 15 |
4 |
| 14 |
3.76 |
| 16 |
3.97 |
| 21 |
3.89 |
| 14 |
3.66 |
| 11 |
3.91 |
| 18 |
3.8 |
| 9 |
3.89 |
6. On the next page is a set of three variables (for each of 20 participants in a study on recovery from a head injury. Create a simple matrix that shows the correlations between each variable. You can do this by hand (and plan on being here for a while), or use SPSS or any other application.
| Age at Injury |
Level of Treatment |
12-Month Treatment Score |
| 25 |
1 |
78 |
| 16 |
2 |
66 |
| 8 |
2 |
78 |
| 23 |
3 |
89 |
| 31 |
4 |
87 |
| 19 |
4 |
90 |
| 15 |
4 |
98 |
| 31 |
5 |
76 |
| 21 |
1 |
56 |
| 26 |
1 |
72 |
| 24 |
5 |
84 |
| 25 |
5 |
87 |
| 36 |
4 |
69 |
| 45 |
4 |
87 |
| 16 |
4 |
88 |
| 23 |
1 |
92 |
| 31 |
2 |
97 |
| 53 |
2 |
69 |
| 11 |
3 |
79 |
| 33 |
2 |
69 |
8. When two variables are correlated (such as strength and running speed), it also means that they are associated with one another. But if they are associated with one another, then why doesn't one cause the other?
1. Go to the library and find five journal articles in your area of interest in which reliability and validity data are reported, and discuss the outcome measures that are used. Identify the type of reliability that was established and the type of validity, and comment on whether you think that the levels are acceptable. If not, how can they be improved?
3. You are developing an instrument that measures vocational preferences (what you want to be), and you need to administer the test several times during the year while students are attending a vocational program. You need to assess the test-retest reliability of the test and the data from two administrations (available as Chapter 6 Data set 1 one in the Fall and one in the spring). Would you call this a reliable test? Why or why not?
| ID |
Scores From Time 1 |
Scores from Time 2 |
| 1 |
54 |
56 |
| 2 |
67 |
77 |
| 3 |
67 |
87 |
| 4 |
83 |
89 |
| 5 |
87 |
89 |
| 6 |
89 |
90 |
| 7 |
84 |
87 |
| 8 |
90 |
92 |
| 9 |
98 |
99 |
| 10 |
65 |
76 |
5. When testing any experimental hypothesis, why is it important that the test you use to measure the outcome be both reliable and valid?