Math and trigonometry
QUARTILE.INC Function
Returns three quartile points from a data set, based on
percentile values from 0 to 1, inclusive. Also returns the
maximum and minimum values.
by
Charley Kyd, MBA Microsoft Excel MVP, 20052014
The Father of Spreadsheet Dashboard Reports

According to WikiPedia, "the quartiles of a ranked set of data values are the four subsets whose boundaries are the three quartile points. Thus an individual item might be described as being 'in the upper quartile'."
Quartiles are used in polling, sociology,
epidemiology, marketing, finance, and other areas of business
and science.
Both QUARTILE.EXE and
QUARTILE.INC return three quartile points that divide a data
set into four quartiles.
QUARTILE is the
deprecated
version of QUARTILE.INC.
Unfortunately...
 There's not a general agreement on
how quartiles should be calculated.
 The different methods that Excel uses with QUARTILE.EXC
and QUARTILE.INC aren't quick and easy to grasp.
If you really need to know how these functions calculate
their differing quartile points, I recommend Jon Peltier's blog
post that I reference in Other Help below. Otherwise,
you might begin with QUARTILE.INC, the deprecated version of the QUARTILE function.
Syntax
QUARTILE.INC(array, quart)

array
Required. The array or cell range of numeric values for
which you want the quartile value.

quart Required.
Indicates which value to return, as shown in the following
table.
If Quart Equals 
QUARTILE.INC Returns 
0 
Minimum value 
1 
First quartile point (25th percentile) 
2 
Median value point (50th percentile) 
3 
Third quartile point (75th percentile) 
4 
Maximum value 
Applies To
Excel 2010 and above
Examples
You can
download this example workbook here,
along with all other example workbooks I've completed for this
Excel help area.
The following examples find the three quartile points then
divide the data into four quartiles plus the three points.
Notice that because some of the points are artificial, they
arent' found in the data.
In practice, you must decide the quartile in which to group a
quartile point that does exist.
Example 1
Example 1 uses an odd number of data points. In this
instance, the quartile points do exist. However, that might not
always be true.
Example 2
Example 2 uses an even number of data points. In this
example, neither quartile point exists. However, that might
always be true.
Other Help
