Loftus and Palmer (1974) conducted a classic study demonstrating how the language used to ask a question can influence eyewitness memory. In the study, college students watched a film of an automobile accident and then were asked questions about what they saw. One group was asked, “About how fast were the cars going when they smashed into each other?” Another group was asked the same question except the verb was changed to “hit” instead of “smashed into.” The “smashed into” group reported significantly higher estimates of speed than the “hit” group. Suppose a researcher repeats this study with a sample of today’s college students and obtains the following results. Estimated Speed Smashed Into Hit n = 15 n = 15 M = 40.8 M = 34.0 SS = 510 SS = 414 a) Do the results indicate a significantly higher estimated speed for the “smashed into” group? Use a one-tailed test with an = .01. (Note: if you are unsure how to do the one-tailed test or use an = .01, you can instead do the two-tailed test with an = .05 and you will reach the same conclusion.) b) Compute the estimated Cohen’s d to measure the size of the effect. c) Write a sentence demonstrating how the results of the hypothesis test and the measure of effect size would appear in a research report.
18)
Loftus and Palmer (1974) conducted a classic study demonstrating how the language used to
ask a question can influence eyewitness memory. In the study, college students watched a film
of an automobile accident and then were asked questions about what they saw. One group was
asked, “About how fast were the cars going when they smashed into each other?” Another
group was asked the same question except the verb was changed to “hit” instead of “smashed
into.” The “smashed into” group reported significantly higher estimates of speed than the “hit”
group. Suppose a researcher repeats this study with a sample of today’s college students and
obtains the following results.
Estimated Speed
Smashed Into Hit
n = 15 n = 15
M = 40.8 M = 34.0
SS = 510 SS = 414
a) Do the results indicate a significantly higher estimated speed for the “smashed into”
group? Use a one-tailed test with an = .01. (Note: if you are unsure how to do the
one-tailed test or use an = .01, you can instead do the two-tailed test with an =
.05 and you will reach the same conclusion.)
b) Compute the estimated Cohen’s d to measure the size of the effect.
c) Write a sentence demonstrating how the results of the hypothesis test and the
measure of effect size would appear in a research report.
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