Chapter 18, Problem 21P

1. In problem 13 in Chapter 17, we Discussed a study by Loftus and Palmer (1974) examining how different phrasing of questions can influence eyewitness testimony. In the study, students watched a video of an automobile accident and then were questioned about what they had seen. One group of participants was asked to estimate the speed of the cars when ''they smashed into each other.” Another group of was asked to estimate the speed of the cars when "the y hit each other.'' Suppose that the actual speed of the cars was 22 miles per hour.
2. For the 50 people in the “smashed-into'' group,
assume that 32 overestimated the actual speed

17 underestimated the speed, I was exactly right. ls this result significantly different from what would be expected by chance? Use a two tailed

test with a = .05.

For the 50 people in the “hit'' group, assume that 27 overestimated the actual speed, 22 underestimated the speed, 1 was exactly right. Again. use a two-tailed test with a = .05 to determine whether

this result significant1y different from what would be expected by chance.

In a classic study, Loftus and Palmer (1974) investigated the relationship between memory for eyewitnesses and the question they are asked.

In the study participants watched a film of an automobile accident and then were questioned about the accident. One group was asked how fast the cars were going when they “smashed into” each other.

A second group was asked about the speed when the car. “Hit” each other, and a third group was not asked any question about the speed of the cars. A week later, the participants returned to answer additional questions about the accident, including whether they recalled. Seeing any broken glass. Although there was no broken glass in the film, several students claimed to remember seeing it. The following table shows the frequency distribution of response for each group.

Response to the Question

Did You See Any Broken Glass?

Verb Used to Ask About the Speed

Verb Used as Ask About t, he Speed

Smashed into Hit

Control (Not Asked)

Response about Broken Glass

Yes: No

1. Does the proportion of participants who claim to remember broken glass differ significantly from group to group? Test with a = .05.
2. Compute Cramer’s V to n1easnfle the size of the
treatment effect.

Describe how the phrasing of the question influ­

enced the participants’ memories.

Write a sentence demonstrating how the outcome of the hypothesis test and the p1easure of effect size would be reported in a journal article.