Chapter 9, Problem 13P

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8th Edition

Frederick J Gravetter + 1 other

ISBN: 9781133956570

Textbook Problem

Standardized measures seem to indicate that the average level of anxiety has increased gradually over the past 50 years (Twenge, 2000). In the 1950s, the average score on the Child Manifest Anxiety Scale was μ = 15.1. A sample of *n* = 16 of today’s children produces a mean score of *M* = 23.3 with *SS* – 240.

**a.** Based on the sample, has there been a significant change in the average level of anxiety since the 1950s? Use a two-tailed test with α = .01.

**b.** Make a 90% confidence interval estimate of today’s population mean level of anxiety.

**c.** Write a sentence that demonstrates how the outcome of the hypothesis test and the confidence interval would appear in a research report.

**a.**

To determine

**To Find:** If there has been a significant change in the average level of anxiety since 1950 using two-tailed test with

Explanation

**Given info:**

A sample of 16 today’s children are selected from a population with mean 15.1. The sample mean, and sum of squared difference (SS) is found to be 23.3 and 240 respectively. Two-tailed hypothesis test using

**Calculations:**

Step 1: Null Hypothesis is

Step 2: For a sample of

Step 3: t-statistics can be calculated using formula:

Calculate

Now, substitute 23

**b.**

To determine

**To Find:** Make a 90% confidence interval estimate for the given question

**c.**

To determine

**To State:** How would the outcome of hypothesis test and confidence interval will appear in the research report.

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