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Standard deviation

The standard deviation is a measure of the spread of the data. As with the mean it comes in a number of flavours.

- Standard deviation of the population

We use this when we know all the outcomes. For example if we have a census (asked everyone) instead of a sample (asked some).

We have

I.e. the standard deviation is the square root of the expected value of the square of the difference between the values and the average.

- Under construction.

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