Question

In a class test where the mean was 62% and the standard deviation 12.6%, bob received 50%. What is his z-score?

Answer 1

`-0.95`

Explanation:

Z-score is the number of standard deviations away from the mean.
So, Bob received 12% less than the mean.

So how many standard deviations is -12%? It is `(12%)/(12.6%)` or -0.95 standard deviations. Thus the z-score is -0.95.

The formal equation for z-score is

where x is the datapoint, x bar is the mean, and s is the standard deviation.