Psychologists have found that people are generally reluctant to transmit bad news to their peers. This phenomenon has been named the "MUM effect." To investigate the cause of the MUM effect, 40 undergraduates at a certain university participated in an experiment. Each subject was asked to administer an IQ test to another student and then provide the test taker with his or her percentile score. (Unknown to the subject, the test taker was a bogus student who was working with the researchers.) The experimenters manipulated two factors, subject visibility and success of test taker, each at two levels. Subject visibility was either visible or not visible to the test taker. Success of test taker was either top 20% or bottom 20%. Ten subjects were randomly assigned to each of the 2 x 2 = 4 experimental conditions, then the time (in seconds) between the end of the test and the delivery of the percentile score from the subject to the test taker was measured. (This variable is called the latency to feedback.) The data was subject to an analysis of variance, with the following results:
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| Subject visibility | 1 | 1380.24 | 1380.24 | 4.25 | 0.430 |
| Test taker success | 1 | 1325.16 | 1325.16 | 4.10 | 0.05 |
| Visibility x success | 1 | 3385.80 | 3385.80 | 10.45 | .002 |
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Which conclusion can you draw from the analysis? Use
α = .01.
◦ At
α = .01, neither subject visibility nor test taker success are important predictors of latency to feedback.
◦ At
α = .01, the model is not useful for predicting latency to feedback.
◦ At
α = .01, there is sufficient evidence to indicate that subject visibility and test taker success interact.
◦ At
α = .01, there is no evidence of interaction between subject visibility and test taker success.
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