# What is the z-score of sample X, if n = 144, mu= 41, St. Dev. =120, and E[X] =63?

The z-score is $= 2.2$
The z-score for a sample mean is $z = \frac{\overline{x} - \mu}{\frac{\sigma}{\sqrt{n}}}$
$= \frac{63 - 41}{\frac{120}{\sqrt{144}}} = \frac{22}{\frac{120}{12}} = \frac{22}{10} = 2.2$