# How do I calculate and interpret a z-score?

##### 1 Answer
Jun 7, 2015

A z-score indicates how many standard deviations a data point is from the mean. It is calculated with the following formula:

z = (X - μ) / σ, where $X$ is the value of tha data point, μ is the mean, and  σ is the standard deviation.
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Besides telling us where a data point lies compared with the rest of the data set in relation to the mean, a z-score also allows comparisons of data points across different normal distributions. (For example, we can compare the scores obtained by a student in two exams whose scores are normally distributed).