Author Question: A research study found that the multiple correlation (R) of three variables (SAT, HS rank, and HS ... (Read 43 times)

biggirl4568 · **on:** Jun 20, 2018

A research study found that the multiple correlation (R) of three variables (SAT, HS rank, and HS GPA) with freshman college GPA was .60 . The researcher would report that

a. the average correlation of each of the variables with college GPA is .20.
b. 60 percent of the variance in college GPA can be explained by the combined variables.
c. 36 percent of the variance in college GPA can be explained by the three variables in combination.

Question 2

Identify the threat to internal validity in each of the following:

a. Some researchers who were given rats to train were told incorrectly that the rats had been bred for intelligence; other researchers were told that their rats were especially dull. The experimenters who had the smart rats reported faster learning than did the experimenters with the dull rats.
b. After the first exam, a professor divided his statistics class into high performers and low performers. The low performers were invited to attend special tutoring sessions where the professor not only reviewed lecture material but also discussed how to take notes and how to study for a statistics test. On the second test, the professor found that the students who received the tutoring improved considerably. The professor concluded that the tutoring sessions were effective in improving the test performance of those students.
c. A researcher divided people attending a weight control clinic into two groups. Both groups were given the same diet to follow, but the experimental group was also asked to keep a record of everything they ate, to weigh all the food in grams, and to count the calories. At the end of the study, the researcher found that the experimental group had lost more weight. The researcher concluded that the experimental treatment was more effective than diet alone.

kjohnson · **Reply #1 on:** Jun 20, 2018

Answer to Question 1

C

Answer to Question 2

a. Experimenter effect
b. Regression; Hawthorne effect
c. Experimental mortality may account for the finding. Because of the greater demands in the experimental group, not all subjects stayed in the program. Only those who were highly motivated to lose weight persisted in the program and were present for the post-treatment.