Examples of population variance and sample variance?

1 Answer
Jun 27, 2018

Population variance is the value obtained IF you are able to measure an attribute of an entire population. It is the average deviation from the actual values from the mean value.


The "Population Variance" is really a hypothetical value, as we rarely are able to measure an entire population. The "Sample Variance" simply takes into consideration the inherent error of not having measured the entire population. It is thus measuring the same thing as a Population Variance, but it is specifically measuring the variation of the observed values from the sample mean value.

A common example is with poll reporting, particularly during elections. When they say that someone has a poll of 45% with a 3% error margin, they usually mean that the variance of the 45 value is +/- 3 (42-48).