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Chapter 3: Measures of Variability
105
Also, the second 50% of the data (excluding
) contains the elements
8, 8, 9, 9, 9, 9, 9, 9, 10.
The median for this set is 9. This corresponds to the value in the 5
th
position. Thus
is 9.
Thus, the interquartile range =
= 9 – 6 = 3. That is, the middle 50
percent of the quiz scores spans a 3-point range.
We can also use the
Basic Statistics
workbook to help compute the quartiles
and the interquartile range for this data set. Note the workbook uses the
procedure described above to determine the
. Observe the data set was
entered in the Data 1 column. The result is shown in
Figure 3-5
.
Figure 3-5:
Computed Interquartile Range for
Example 3-4
The quartiles and interquartile range are also given in
Figure 3-6
. These
were also generated by the
Basic Statistics
workbook as well.
Figure 3-6:
Computed Quartiles and Interquartile Range
for
Example 3-4
Click here for the Basic Statistics Workbook