Question

The scores on a test are normally distributed with a mean of 78 and a standard deviation of 13. Find the score that is 2 standard deviations below the mean

Answer 1

52

Explanation:

Given that :

Mean (m) = 78

Standard deviation (s) = 13

Score that is 2 standard deviations below the mean

Using the relation :

Zscore = (x - m) / s

2 standard deviations below the mean means a Zscore of - 2

Hence,

-2 = (x - 78) / 13

Cross multiply

-2 * 13 = x - 78

-26 = x - 78

x = - 26 + 78

x = 52

Score which is 2 standard deviations below the mean is 52