Chapter 9 Solutions

Chapter 8 Solutions

Chapter 7 solutions

Solutions to Confidence Interval Questions from the Book

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Solutions provided thanks to Semih.

Practice Questions - Hypothesis testing

1. For each situation, find the z (critical).
1. α = 0.05 One tailed
2. α = 0.10 Two tailed
2. For each situation find the t (critical)
1. α = 0.10, two tailed, N = 31
2. α = 0.02, two-tailed, N = 24
3. α = 0.01, one-tailed, N = 31
3. Compute the appropriate test statistic (Z or t) for each situation:
1. µ = 2.40; σ = 0.75; Xbar (sample mean) = 2.20; N = 200
2. µ = 17.1; Xbar = 16.8; s = 0.9; N = 45
3. µ = 10.2; Xbar = 9.4; s = 1.7; N = 150
4. Nationally the average score on the college entrance exams is 453 with a standard deviation of 95. A random sample of 152 freshmen entering St Statistics University shows a mean score of 502. Is there a significant difference?
5. A random sample of 113 convicted rapists in a prison system completed a program designed to change their attitudes toward women, sex and violence before being released. 58 eventually become repeat sex offenders. Is this repeat rate significantly different from the rate of all offenders in this prison system (57%). Summarize your conclusions in a sentence or two.

The t table

Practice Questions - Interval Estimation

Estimation and confidence intervals

1. For each set of sample outcomes below, construct the 95% confidence interval for estimating µ, the population mean.
1. Sample mean = 5.2; s = 0.7; N = 157
2. Sample mean = 1020; s = 50; N = 329
3. Sample mean = 100; s = 9; N = 120
2. You have developed a series of questions to measure the “burnout” in social workers. A random sample of 100 social workers working in the city have an average score of 10.3, with a standard deviation of 2.7. What is your estimate of the average burnout score for the population as a whole? Use the 95% confidence level.