## 1.13 Z-score

The z-score is the number of standard deviations by which the value of an observation or data point is above the mean value of what is being observed or measured. For example, if the mean of the data is 50 and the standard deviation is 10, then a z-score of 1.5 indicates that the data point is 15 above the mean. Mathematically, the z-score is calculated as follows: \[z = \frac{x - \mu}{\sigma}\] where \(x\) is the data point, \(\mu\) is the mean, and \(\sigma\) is the standard deviation. Z-scores are also useful for comparing data from different groups.