120 / 762
120
Chapter 3: Measures of Variability
Figure 3-15:
Display with Sample Variance and
Standard Deviation for
Example 3-10
We can also compute the variance and standard deviation for a finite
population of values.
Definition: Population Variance
The population variance is the average of the squared deviations of the data
values from the population mean.
That is, the deviations of the data values from the population mean are first
computed, then the values for these deviations are squared, and then the
average of these square values is found. The average will be exact because
we divide by the population size.
Generally, if there are
data values in the population, with
x
representing
the data values, and
being the population mean, then the population
variance, denoted by
(read as “sigma squared”) is given by