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Chapter 3: Measures of Variability
117
Next, we will build a table to help with the computations.
Table 3-2
displays the data values, the deviations from the sample mean, and the
square deviations.
Table 3-2:
Table Used in Helping to
Compute the Sample Variance for
Example 3-8
The table illustrates why we square the deviations. As the second column
shows, the sum of the deviations is equal to zero. Squaring the deviations
yields a positive value. Using the information produced in the table, we can
substitute into the sample variance formula to get the required value.
Since the
∑( ̅
)
then,
( )
( )
.
Using the
Basic Statistics
workbook, observe the value of the sample
variance is 26.4 as well. This is shown in
Figure 3-14
when the values are
entered into the Data 1 column.