Understanding Z-score

Another way to represent a range of acceptable values is using a z-score. Z-score, sometimes called standard score, is the number of standard deviations from the mean. In the previous section, our acceptable range was one standard deviation from the mean, or in other words, a z-score in the range ±1:

Like before, we can detect anomalies by searching for values that are outside the acceptable range using the z-score:

Using the z-score, we identified 12 as an anomaly in this series.