Use an independent-measures t test with α=.05 to determine whether there is a significant difference between the two conditions and compute r2 to measure effect size. Now, increase the variability by doubling the two SS values to SS1=1,020 and SS2=828. Repeat the hypothesis test and the measure of effect size. Comparing your answers for Parts a and b, describe how sample variability influences the outcome of the hypothesis test and the measure of effect size.
In 1974, Loftus and Palmer 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=15M=40.8SS=510 |
n=15M=34.9SS=414 |
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Use an independent-measures t test with α=.05 to determine whether there is a significant difference between the two conditions and compute r2 to measure effect size.
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Now, increase the variability by doubling the two SS values to SS1=1,020 and SS2=828. Repeat the hypothesis test and the measure of effect size.
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Comparing your answers for Parts a and b, describe how sample variability influences the outcome of the hypothesis test and the measure of effect size.
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