# A Statistical Background

Last update: Thu Oct 22 16:46:28 2020 -0500 (54a46ea04)

## A.1 Basic statistical terms

### A.1.1 Five-number summary

The five-number summary consists of five values: minimum, first quantile, second quantile, third quantile, and maximum. The quantiles are calculated as:

• first quantile ($$Q_1$$): the median of the first half of the sorted data
• third quantile ($$Q_3$$): the median of the second half of the sorted data

First quantile: 25th percentile. Second quantile: 50th percentile. Third quantile: 75th percentile.

The interquartile range or IQR is defined as $$Q_3 - Q_1$$ and is a measure of how spread out the middle 50% of values is.