152 Fundamentals of Statistics
QUARTILE(array, quart) Returns the quartile of an array of values or range
reference, where quart is either 1, 2, or 3 for the fi rst,
second, or third quartile.
IQR(array) Calculates the interquartile range of the values in an
array or range reference. StatPlus required.
Excel allows you to work with percentiles in two different ways. You can
use the PERCENTILE function to take a percentile and determine the corre-
sponding data value, or, given the data value, you can use the PERCENTRANK
function to determine its percentile.
You can create a table of percentile and quartile values by typing in
the above Excel formulas, or you can have StatPlus do it for you with the
Univariate Statistics command. The Univariate Statistics command also
allows you to break down the variable into different levels of a categorical
variable.
In this example you’ll limit yourself to percentiles and quartiles. Create
such a table now of the housing prices broken down by location.To create a table of percentile and quartile values:1 Click Descriptive Statistics from the StatPlus menu and then click
Univariate Statistics.
2 Click the Input button and select Price from the list of range names.
3 Click the Output button, click the New Worksheet option but-
ton, and type Percentiles in the New Worksheet box. Click the OK
button.
4 Click the By button and select NE_Sector from the list of range
names.
5 Click the Distribution dialog tab.
6 Click each of the checkboxes for the different percentiles. See
Figure 4-15.