In statistics, an outlier is a data point that differs significantly from other observations.

An outlier may be due to variability in the measurement or it may indicate experimental error.

**Formula to calculate outlier.**

For the higher outlier we use the following formula.

For the lower outlier we use;

Q1 is the lower quartile.

Q3 is the upper quartile.

IQR is the interquartile range.

**Example:**

Suppose you had a data set and you calculated your lower quartile to be 5 and your upper quartile to be 60. If your interquartile range is 55, calculate your lower outliers.

Therefore, your lower outlier is -77.5.