A social psychologist interested in attitude change ran the following study. University students were asked to evaluate the quality of a passage of poetry on a 21-point scale and then listened to a taped message concerning the passage that was presented as representing the opinion of either an expert (a famous poetry critic) or a non-expert (an undergraduate student taking beginners’ English). The messages were identical, the only difference being the source they were attributed to (either the expert or the non-expert). In addition, the messages were constructed to be either slightly discrepant, moderately discrepant, or highly discrepant from subjects’ initial ratings of quality. For example, in the large discrepancy condition, if a subject rated the passage as being relatively high in quality, the message argued that the passage was low in quality. After listening to the message, subjects rerated the poetry. The resulting design was a 2 x 3 factorial design with two levels of source expertise (high and low) and three levels of message discrepancy (small, medium, or large). The dependent variable was the amount of change in the quality ratings after listening to the message. Scores could range from –20 to +20, with higher scores indicating greater attitude change in the direction advocated by the source. Five subjects were randomly allocated to each of the six cells of the design. Data are given below:

Small Discrepancy/High Expertise: 3 4 2 3 3

Small Discrepancy/Low Expertise: 1 0 2 1 1

Medium Discrepancy/High Expertise: 6 5 5 5 4

Medium Discrepancy/Low Expertise: 3 2 3 4 3

Large Discrepancy/High Expertise: 5 4 6 5 5

Large Discrepancy/Low Expertise: 0 1 1 2 1

Put the data into a relevant SPSS file and perform analyses in SPSS in order to answer the questions below (contrasts may be performed by hand).

1. Is there any evidence to suggest that attitude change depends on source of expertise, averaged across discrepancy? Provide statistics that justify your answer, and comment on the direct ion of any attitude change.
2. What critical value is used to evaluate the main effect of discrepancy?
3. The researcher wishes to test a contrast comparing the small and medium discrepancy conditions. What sum of squares is associated with such a contrast?
4. Perform the overall test for the interaction effect. What are the results of this overall test, and what conclusions follow?
5. Assuming a post-hoc design test any interaction contrasts that seem sensible. What conclusions follow from this contrast testing?

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