Quartiles:



Quartiles:

If a data set of values is arranged in ascending order of magnitude, then:

• The median is the middle value of the data set.

[pic]

• The lower quartile (Q1) is the median of the lower half of the data set.

[pic]

• The upper quartile (Q3) is the median of the upper half of the data set.

[pic]

• The interquartile range (IQR) is the spread of the middle 50% of the data values.  So:

 The interquartile range is a more useful measure of spread than the range as it describes the middle 50% of the data values

Example

Find the median, lower quartile, upper quartile and interquartile range of the following data set of scores:

18     20     23     20     23     27     24     23     29

Solution:

Arrange the values in ascending order of magnitude:

18     20     20     23     23     23     24     27     29

There are 9 values in the data set.

[pic]

[pic]

[pic]

[pic]

[pic]

This means the middle 50% of the data values range from 20 to 25.5.

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download