This can be used in the case where the data is available for the whole population under consideration. The population variance refers to the variance of all datapoints. This simple measure is useful, alongside the mean, of quickly describing the properties of any normally-distributed distribution.
The yellow line shows a higher variance, within which the data is much more likely to have a value of 3 than the blue distribution. The blue, red and yellow lines represent distributions with the same mean, but different variances. In the case of the normal distribution, the variance is squared standard deviation (σ^2). It shows the 'spread' of a distribution, with higher variance representing an increased likelihood of values that are further from the mean. When looking at a distribution in a dataset, variance is a key feature.
