Variance is a statistical measure of how closely or widely the individual points in a set of data are dispersed. In simple terms, it measures the average difference between an individual results and the overall average result. It can help put data into context and identify possible errors, but in its raw form can be difficult to comprehend in a meaningful way.

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## Calculation

To calculate variance, add up the individual figures (data points), then find the mean average. For each individual data point, you then find the difference between the data point and the mean average, then square this difference. Repeat this process for each data point, then calculate the mean average of all the squared differences.

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Finding the variance in a data set can give a useful insight into the group covered by the data set. For example, if the data covers ages of television viewers in a particular region, a low variance means station controllers can safely concentrate on airing shows aimed at a particular age group. A high variance would mean such a strategy would be unlikely to work.

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