Elementary Statistics: A Step-by-Step Approach with Formula Card 9th Edition

Published by McGraw-Hill Education
ISBN 10: 0078136334
ISBN 13: 978-0-07813-633-7

Chapter 7 - Confidence Intervals and Sample - 7-2 Confidence Intervals for the Mean When σ Is Unknown - Exercises 7-2 - Page 387: 7

Answer

$21.2\lt\mu\lt45.6$ see explanations.

Work Step by Step

1. Based on the data set we can find $\bar X=33.4, s=28.7 , n= 17$ 2. At the 90% confidence and $df=16$, the critical t-value is $t_{\alpha/2}=1.75$ (use table F) 3. The margin of error can be found as $E=1.75\times\frac{28.7}{\sqrt {17}}=12.2$ 4. Thus, the interval of the true mean can be estimated as $\bar X-E\lt\mu\lt\bar X+E$ which gives $21.2\lt\mu\lt45.6$ 5. The population mean (about 32) is close to the point estimate of $\bar X$ and is contained in the confidence interval. 6. One data point (132) is unusual because it is an outlier which may have shifted the point estimate and the confidence interval higher.
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