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 15 15M 40.8 34.9SS 510 414Do the results indicate significant difference in estimated speed between the two groups? Use a two-tailed test with α = .05.Pooled Variance? Estimated Standard Error? t Statistic? Critical Values? Which is correct?Fail to reject H₀. These data do not indicate a significant difference in estimated speed between the two groups.Reject H₀. These data do not indicate a significant difference in estimated speed between the two groups.Reject H₀. These data indicate a significant difference in estimated speed between the two groups.Fail to reject H₀. These data indicate a significant difference in estimated speed between the two groups. Compute r² to measure effect size.r² = 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.Pooled Variance?Estimated Standard Error?t Statistic?Critical Values? Reject H₀. These data indicate a significant difference in estimated speed between the two groups.Fail to reject H₀. These data do not indicate a significant difference in estimated speed between the two groups.Fail to reject H₀. These data indicate a significant difference in estimated speed between the two groups.Reject H₀. These data do not indicate a significant difference in estimated speed between the two groups.r² = Comparing your answers for the preceding parts, describe how sample variability influences the outcome of the hypothesis test and the measure of effect size.Increasing the sample variability the likelihood of rejecting the null hypothesis and the size of r².
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 15 15
M 40.8 34.9
SS 510 414
Do the results indicate significant difference in estimated speed between the two groups? Use a two-tailed test with α = .05.
Pooled Variance?
Estimated Standard Error?
t Statistic?
Critical Values?
Which is correct?
Fail to reject H₀. These data do not indicate a significant difference in estimated speed between the two groups.
Reject H₀. These data do not indicate a significant difference in estimated speed between the two groups.
Reject H₀. These data indicate a significant difference in estimated speed between the two groups.
Fail to reject H₀. These data indicate a significant difference in estimated speed between the two groups.
Compute r² to measure effect size.
r² =
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.
Pooled Variance?
Estimated Standard Error?
t Statistic?
Critical Values?
Reject H₀. These data indicate a significant difference in estimated speed between the two groups.
Fail to reject H₀. These data do not indicate a significant difference in estimated speed between the two groups.
Fail to reject H₀. These data indicate a significant difference in estimated speed between the two groups.
Reject H₀. These data do not indicate a significant difference in estimated speed between the two groups.
r² =
Comparing your answers for the preceding parts, describe how sample variability influences the outcome of the hypothesis test and the measure of effect size.
Increasing the sample variability the likelihood of rejecting the null hypothesis and the size of r².
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