# Z-scores

Z-score tells you how different is a value from the mean (normal) in terms of standard deviation. It is calculated as (X – Mean)/ Standard Deviation

**Why it matters:** Z-scores or standard scores are used to find out what is special.

- In a dataset that is normally distributed, 95.45% of the data falls in 2 standard deviations from the mean. Hence, there is less than 5% chance for Z-score to be higher than 2 in such a dataset.

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