Chapter 10, Problem 18P

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8th Edition

Frederick J Gravetter + 1 other

ISBN: 9781133956570

Textbook Problem

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.

a. Do the results indicate a significantly higher estimated speed for the “smashed into” group? Use a one-tailed test with

b. Compute the estimated value for 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 n research report.

**a.**

To determine

Whether the result indicate a significantly higher estimated speed for the “smashed into” group using one-tailed test with
α = 0.01 .

Explanation

**Given info:**

Two samples each with size 15 have means 40.8 and 34 respectively. The sum of squared difference (SS) is 510 and 414 respectively.

**Calculations:**

Step 1: Null hypothesis is

Step 2: For the give sample, degrees of freedom is calculated as:

For one-tailed test with

Step 3: *t*-statics is calculated using formula:

Pooled variance

**b.**

To determine

**To find:** The value of Cohen’s d.

**c.**

To determine

The outcome of study the way it would be reported.

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