Dr. Phil wanted to see whether sex, drugs, or rock and roll improved student self-esteem more than traditional counseling or no treatment at all over a six-week period. He randomly assigned four groups of 30 students to two groups. In all four groups the control group received no special treatment.
In Experimental Group A he gave the students favorable information about illegal drug use, supplied them with quantities of several types of illegal drugs free of charge, and encouraged them to try the drugs.
In Experimental Group B he told the students about the history of rock and roll and gave them portable stereo players with a large quantity of rock and roll music. He also encouraged them to listen to the music at least six hours per day.
In Experimental Group C he told the students the benefits of premarital sex and encouraged them to experiment with sexual behavior. He introduced them to attractive members of the opposite sex who had very liberal sexual attitudes. He also supplied them with contraceptives and private rooms.
In Experimental Group D he placed the students in traditional counseling to improve their self-esteem.
NOTE: He measured self-esteem with a questionnaire in which self-esteem went from 0 = very negative to 100 = very positive.
Self Esteem Score and (Number of Students) – For example, in the experimental group within set A, 15 students took the pretest and received an average self-esteem score of 65. In the control group within set A, 15 students took the pretest and received an average self-esteem score of 60. In the experimental group within set A, 13 students took the posttest and received an average score of 63. In the control group within set A, 14 students took the posttest and received an average score of 66.
Self Esteem Score and (Number of Students)
Sets Groups Pretests Posttests
A Experimental 65 (15) 63 (13)
Control 60 (15) 66 (14)
B Experimental 65 (15) 89 (14)
Control 45 (15) 79 (14)
C Experimental 66 (15) 90 (6)
Control 65 (15) 67 (14)
D Experimental 64 (15) 88 (14)
Control 63 (15) 66 (15)
1. Which set’s findings suggest that differential attrition may be an issue?
a. Set A
b. Set B
c. Set C
d. Set D
2. Which set suggests that internal validity is not a noticeable problem and the independent variable had an effect?
a. Set A
b. Set B
c. Set C
d. Set D
3. Which set suggests an initial problem of selection bias?
a. Set A
b. Set B
c. Set C
d. Set D
4. What was the problem with the findings identified in Set A?
a. The independent variable does not appear to have an empirical association with the dependent variable.
b. The independent variable did not have the proper time order to demonstration causation.
c. There is a clear spurious variable which is causing changes in both the independent and dependent variable.
d. Regression
e. Treatment Misidentification
5. Laboratory experiments tend to have better internal validity and less external validity than field experiments.
a. True
b. False
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