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Statistics for Six Sigma Green Belts with Minitab and JMP by David M. Levine

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4.2. Measures of Variation

A second important property that describes a set of numerical data is variation. Variation is the amount of dispersion, or spread, in a set of data, be it a sample or a population. Three frequently used measures of variation are the range, the variance, and the standard deviation.

The Range

The range is the simplest measure of variation in a set of data.

Range

The range is equal to the largest value minus the smallest value:

Range = largest value – smallest value (4.5)

Using the data pertaining to the time to get ready in the morning on page 43:

Range = largest value – smallest value

Range = 52 – 29 = 23 minutes

This means that the largest difference between any two days in the time to get ready in the morning ...

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