How to Find Quartiles with QUARTILE.INC

Split data into quarters with QUARTILE.INC, measure the interquartile range and set an outlier fence.

You will learn to

• Find the first quartile with QUARTILE.INC
• Calculate the interquartile range (IQR)
• Build the 1.5×IQR upper outlier fence

How it works

QUARTILE.INC(array, quart) returns the minimum (0), first quartile (1), median (2), third quartile (3) or maximum (4). Q1 is the value 25% of the data falls below; Q3 is the 75% point. The gap Q3 − Q1 is the interquartile range (IQR): the spread of the middle half of the data, unaffected by extreme values.

The IQR is the basis of the box-plot outlier rule: anything above Q3 + 1.5×IQR (or below Q1 − 1.5×IQR) is unusually far from the rest and worth investigating.

=QUARTILE.INC(C2:C12,1)