Percentages
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Question

A data set is normally distributed with the mean value $\mu = 63.00$ and standard deviation $\sigma = 9.00$. What percentage of data values are less than $x = 58.00$

z-score of $x=58.00 = z = \frac{x-\mu}{\sigma} = \frac{58.00 - 63.00}{9.00}=-0.56$
The area under the standard normal distribution curve to the left of $z=-0.56$ is $0.2877$
The percentage of data values that are less than $x=58.00$ is $28.77$