Chapter 8.3, Problem 79E

a)

To determine

To find sample standard deviation.

Answer to Problem 79E

The sample standard deviation is 91.2547 mm

Explanation of Solution

Given:

  $\begin{array}{l}Standarderror=SE=19.03\hfill \\ Samplemean=\overline{x}=61.55\hfill \\ Samplesize=n=23\hfill \end{array}$

Formula:

Standard error:

  $SE=\frac{s_x}{\sqrt{n}}$

Calculation:

Using the formula,

  $\begin{array}{l}19.03=\frac{s_x}{\sqrt{23}}\\ s_x=19.03\times \sqrt{23}\\ s_x=91.2647\end{array}$

b)

To determine

To find the actual confidence level.

Answer to Problem 79E

The actual confidence level is 66%

Explanation of Solution

Given:

  $\begin{array}{l}Standarderror=SE=19.03\hfill \\ Samplemean=\overline{x}=61.55\hfill \\ \begin{array}{l}Samplesize=n=23\\ Criticalt*=1\end{array}\hfill \end{array}$

Calculation:

The degrees of freedom =df = n-1= 23-1 = 22

Therefore, the confidence level can be found using excel formula,

=2*TDIST(1,22,2)

So confidence level = 66%