Solution Found!
The following sample of 16 measurements was selected from
Chapter 6, Problem 28E(choose chapter or problem)
The following sample of 16 measurements was selected from a population that is approximately normally distributed:
\(\begin{array}{rrrrrrrrrrrr}
\hline 91 & 80 & 99 & 110 & 95 & 106 & 78 & 121 & 106 & 100 & 97 & 82 \\
100 & 83 & 115 & 104 & & & & & & & & \\
\hline
\end{array}\)
a. Construct an 80% confidence interval for the population mean.
b. Construct a 95% confidence interval for the population mean and compare the width of this interval with that of part a.
c. Carefully interpret each of the confidence intervals and explain why the 80% confidence interval is narrower.
Questions & Answers
QUESTION:
The following sample of 16 measurements was selected from a population that is approximately normally distributed:
\(\begin{array}{rrrrrrrrrrrr}
\hline 91 & 80 & 99 & 110 & 95 & 106 & 78 & 121 & 106 & 100 & 97 & 82 \\
100 & 83 & 115 & 104 & & & & & & & & \\
\hline
\end{array}\)
a. Construct an 80% confidence interval for the population mean.
b. Construct a 95% confidence interval for the population mean and compare the width of this interval with that of part a.
c. Carefully interpret each of the confidence intervals and explain why the 80% confidence interval is narrower.
ANSWER:Step 1 of 4:
We have 16 samples selected from the population
\(\begin{array}{|l|l|} \hline \mathrm{X} & x^{2} \\ \hline 91 & 8281 \\ \hline 80 & 6400 \\ \hline 99 & 9801 \\ \hline 110 & 12100 \\ \hline 95 & 9025 \\ \hline 106 & 11236 \\ \hline 78 & 6084 \\ \hline 121 & 14641 \\ \hline 106 & 11236 \\ \hline 100 & 10000 \\ \hline 97 & 9409 \\ \hline 82 & 6724 \\ \hline 100 & 10000 \\ \hline 83 & 6889 \\ \hline 115 & 13225 \\ \hline 104 & 10816 \\ \hline \Sigma x=1567 & \Sigma x^{2}=155867 \\ \hline \end{array}\)
\(\begin{aligned} \text { Mean } & =\frac{\Sigma x_{i}}{n} \\ & =\frac{1567}{16} \\ & =97.9375 \end{aligned}\)
\(\begin{aligned} \text { Variance } & =\frac{\Sigma x^{2}-\frac{(\Sigma x)^{2}}{n}}{n-1} \\ & =\frac{155867-\frac{(1567)^{2}}{16}}{16-1} \\ & =\frac{155867-153468.0625}{15} \\ & =159.9291 \end{aligned}\)
\(\begin{aligned} \sigma & =\sqrt{159.9291} \\ & =12.6431 \end{aligned}\)