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Problems and Exercises I
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Experiments with Repeated Measures Designs

Read the summaries of the experiments below and answer the questions that follow.



Description:

A psychologist believes that people are either "auditory learners" or "visual learners." Specifically, she thinks some people remember information better when it is presented auditorily and others remember information better when it is presented visually. She tests her theory by asking undergraduate students to study and remember a list of words presented on a tape recorder (auditory) or on a sheet of paper (visual). To find out whether people are primarily auditory or visual learners, one week prior to the experiment a colleague asks students in a large introductory psychology class to fill out a long, involved questionnaire about attitudes, beliefs, etc. Buried in the questionnaire is a question about the student’s most preferred mode of learning, that is, visual or auditory. When students come later for the memory experiment, two different lists of 20 words are presented for study. Unknown to the students, the psychologist uses the information from the questionnaire to identify which mode of presentation is preferred by each student. Each student is tested first under his or her preferred mode of study and then under his or her non-preferred mode. Although the manner in which the words are presented changes for each student, everything else is held constant. That is, the same 20 words are always used for the preferred mode of presentation and for the non-preferred mode of presentation, the length of time the words are presented is the same, as is the retention interval, and so forth. The psychologist finds that the average recall in the preferred mode is significantly better than the average recall under the non-preferred mode. She believes the results support her hypothesis.



1

Identify the (a) independent variable and the (b) dependent variable in this experiment.
2

Identify two serious confoundings in this experiment.
3

Describe how the experiment should be conducted, that is, state specifically how the confoundings could be eliminated.

Description:

A developmental psychologist believes that the more television violence children see, the less they are affected by it. To test his hypothesis he selects 24 two-minute cartoon episodes that vary in the amount of violence. He measures violence based on a formula using the number of "hits" and "kills." Each episode is scored according to the violence formula so that he is able to rank order the 24 episodes from most violent to least violent. He then selects the six most violent episodes. These six episodes are arranged in a random order and prepared for television viewing to 18 preschool children. The children are tested individually. After viewing each video episode, he asks each child several questions about the content of the video. From these answers the psychologist computes a "comfort" index, purportedly revealing how comfortable the child was when viewing the video. The psychologist predicted that the children would become more comfortable as they viewed more of the violent videos. In fact, his results support his hypothesis. Average comfort ratings increased systematically as the number of episodes viewed increased.



4

How is "violence" operationally defined in this experiment?
5

A critical reviewer of this study would likely want to know about the reliability of both the violence classification and the "comfort" index. Explain how reliability could be assessed for these two measures.
6

The same critical reviewer probably would raise questions about experimenter bias. (a) Suggest how experimenter bias could play a role in this experiment, and (b) describe what could be done to control experimenter bias (expectancy effects).
7

Comment briefly on possible limitations on the external validity of this experiment in terms of the materials that were used.
8

Explain why the results of this experiment should not be considered seriously. Identify as specifically as you can what aspects of this study prevent an unambiguous interpretation of the researcher's findings.





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