Creating a Moving Range chart
A Moving Range (mR) chart is a way of monitoring variation to try and work out if a system is varying unexpectedly.
The range is simply calculated as the absolute difference between one data point and the previous one. We then calculate an average—usually over a specific subset of the data—of these values and apply a statistical constant (3.267 - D4 anti-biasing constant for a subgroup size of n=2). The great thing about these constants is that you don't need to understand them or how they are calculated; just that they exist.
In this recipe, we are going to use the same set of rainfall data as the previous recipe, Creating a Statistical Control Chart using Standard Deviation, to see how the rainfall data for Heathrow ...
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