91影视

The mean is $\mathrm{渭}=13$and standard deviation is $\mathrm{蟽}=9$

The number of customers

The sample mean $\stackrel{炉}{\mathrm{x}}=15$

The following concept was used:

$\mathrm{z}=\frac{\mathrm{x}鈭�{\mathrm{渭}}_{\stackrel{炉}{\mathrm{x}}}}{{\mathrm{蟽}}_{\stackrel{炉}{\mathrm{x}}}}$

The sampling distribution of the sample mean $\stackrel{炉}{\mathrm{x}}$is also normal because the population distribution is normal.

Z-score is $\mathrm{z}=\frac{\mathrm{x}鈭�{\mathrm{渭}}_{\stackrel{炉}{\mathrm{x}}}}{{\mathrm{蟽}}_{\stackrel{炉}{\mathrm{x}}}}=\frac{\stackrel{炉}{\mathrm{x}}鈭�\mathrm{渭}}{{\displaystyle \frac{\mathrm{蟽}}{\sqrt{\mathrm{n}}}}}=\frac{15鈭�13}{{\displaystyle \frac{9}{\sqrt{40}}}}=1.41$

Using the normal probability, the associating probability is calculated.

$\mathrm{P}\left(\mathrm{Z}<1.41\right)$is typical normal probability table in the appendix has a row beginning with 1.4 and a column beginning with .01.

$\begin{array}{c}\mathrm{P}\left(\stackrel{炉}{\mathrm{X}}鈮�15\right)=\mathrm{P}\left(\mathrm{Z}>1.41\right)\\ =1鈭�\mathrm{P}\left(\mathrm{Z}<1.41\right)\\ =1鈭�0.9207\\ =0.0793\\ =7.93\text{\%}\end{array}$

The mean is $\mathrm{渭}=13$and standard deviation is$\mathrm{蟽}=9$

The number of customers $\mathrm{n}=40$

$\mathrm{P}\left(\stackrel{炉}{\mathrm{X}}鈮�\stackrel{炉}{\mathrm{x}}\right)=95\mathrm{\%}$

The following concept was used:

$\mathrm{z}=\frac{\mathrm{x}鈭�{\mathrm{渭}}_{\stackrel{炉}{\mathrm{x}}}}{{\mathrm{蟽}}_{\stackrel{炉}{\mathrm{x}}}}$

Determine the z-score that corresponds to a probability of 95 percent or 0.95 in the normal probability table and The probability 0.95 lies exactly between 0.9495 and 0.9505, where the z-scores 1.64 and 1.64 correspond to the probability 0.95, which is 1.645.

$\mathrm{z}=1.645$

Z-score is $\mathrm{z}=\frac{\mathrm{x}鈭�{\mathrm{渭}}_{\stackrel{炉}{\mathrm{x}}}}{{\mathrm{蟽}}_{\stackrel{炉}{\mathrm{x}}}}=\frac{\stackrel{炉}{\mathrm{x}}鈭�\mathrm{渭}}{{\displaystyle \frac{\mathrm{蟽}}{\sqrt{\mathrm{n}}}}}=\frac{15鈭�13}{{\displaystyle \frac{9}{\sqrt{40}}}}=1.41$

The z-two score's found expressions must then be equal:

$\frac{\stackrel{炉}{x}鈭�13}{\frac{9}{\sqrt{40}}}=1.645$

Each side should be multiplied by a $\frac{9}{\sqrt{40}}$

$\stackrel{炉}{\mathrm{x}}鈭�13=1.645\left(\frac{9}{\sqrt{40}}\right)$

To each side, add 13:

$\stackrel{炉}{\mathrm{x}}+13=1.645\left(\frac{9}{\sqrt{40}}\right)$

Determine:

$\mathrm{x}=15.34$

As a result, the business should charge is 15.34