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Question

A data set is normally distributed with the mean value $\mu = 78.00$ and standard deviation $\sigma = 19.00$. What percentage of data values are less than $x = 39.00$

Answer

z-score of $x=39.00 = z = \frac{x-\mu}{\sigma} = \frac{39.00 - 78.00}{19.00}=-2.05$

The area under the standard normal distribution curve to the left of $z=-2.05$ is $0.0202$

The percentage of data values that are less than $x=39.00$ is $2.02$