Exam 8: Experimental Designs

A field experiment on labor market discrimination (Box 8.1) showed that white applicants with a high-quality resume were more likely to be called back for an interview than whites with a low-quality resume but that quality of resume made no difference in whether African-American applicants were called back for interviews. This outcome indicates

Suppose you want to test the effects of handing out free samples of pizza on the sales of frozen pizza in supermarkets. For one week, you provide free samples in a "test" supermarket located in one area and do not provide free samples in a "control" supermarket located in another area. During this period a pizzeria located in the test area goes out of business. If you found that pizza sales increased in the test store but not in the control store, what is a likely alternative explanation to the effect of providing free hot pizza?

Which of the following sets of findings is an example of an interaction effect?

A study is designed to test the effectiveness of a program to teach adolescents about nutrition. All research participants are randomly assigned to two groups, one which goes through the program and the other which does not. Both before and after the program, all participants take a test measuring knowledge of nutrition. What type of experimental design is this?

Suppose the effects of a treatment are tested in two different experiments. Experiment A consists of a pretest-posttest, control group design; experiment B consists of a posttest-only, control group design. The treatment is found to have an effect only in experiment A. A One possible explanation of the discrepancy in findings is the effects of __________ in experiment

2. A large cooperation develops a long-term project to test a series of leadership training courses it is designing. The training courses are to be offered after work for low-level employees. They will be run on a volunteer basis, and the workers will not be paid for staying late to attend. To evaluate the effectiveness of the course after ten years, the corporation decides that the measure of effectiveness will be how many of the individuals who take the course assume positions of leadership in comparison with those who did not take the course. a. What is the measure of the dependent variable in this study? b. In words or appropriate notation, identify the design of the study. c. Assume that after ten years it is found that those who took the leadership course are more likely to be in positions of leadership within the corporation than those who did not. Identify two threats to internal validity and carefully explain how each could account for this effect.

A study lacks __________ if it fails to eliminate the possibility that an extraneous variable rather than the independent variable produced the effect on the dependent variable.

Which of the following is an example of a true experimental design?

A major threat to the internal validity of the interrupted time-series design is history.

"Interaction effect" refers to the social relations among subjects that take place in most experiments.

The Solomon four-group design may be construed as a 2 × 2 factorial design.

The separate-sample pretest-posttest design

In a laboratory experiment on helping behavior, two variables are manipulated: (1) others' presence (whether participants worked alone on a task or with others) and (2) type of task (whether participants were timed or untimed on the task). The dependent measure is the number of seconds between someone's request for help and the participant's response. What type of experimental design is this?

Counterbalancing in within-subjects designs controls for the effects of

The basic principle of good experimental design is allowing only one factor to vary at a time.

If a study has all the features of a true experiment, any difference between conditions (e.g., a treatment group and a control group) may be due to the manipulation of the independent variable and/or to

The posttest-only control group design generally is preferred over the pretest-posttest control group design because the latter is susceptible to the effects of

Which feature of a true experiment is missing from the nonequivalent control group design?

The two factors that are varied in a Solomon four-group design are

Which threat to internal validity is controlled by randomly assigning research participants to experimental conditions?