# What is the z-score of sample X, if n = 196, mu= 45, St. Dev. =28, and E[X] =40?

$z = - \frac{5}{2} = - 2.5$

#### Explanation:

Use the formula

$z = \frac{x - \mu}{\frac{\sigma}{\sqrt{n}}}$

$z = \frac{40 - 45}{\frac{28}{\sqrt{196}}}$

$z = - \frac{5}{2}$

$z = - 2.5$

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