# What is the z-score of X, if n = 135, mu= 74, SD =3, and X =73?

Jan 23, 2016

$Z = \frac{73 - 74}{\frac{3}{\sqrt{135}}} = - \frac{\sqrt{135}}{3}$

#### Explanation:

The standard normal distribution simply converts the group of data in our frequency distribution such that the mean is 0 and the standard deviation is 1.

We can use: $z = \frac{x - \mu}{\sigma}$ assuming we have $\sigma$
but here we have instead SD = s;

$z = \frac{x - \mu}{\frac{s}{\sqrt{n}}}$; where n is sample size...