Summary of formulae for plotting four basic control charts
Type of dataType of chartCentre lineThree-sigma control limits
Continuous data (x) of which there are n itemsx-chartEmbedded ImageEmbedded Image
mr-chartEmbedded ImageEmbedded Image
Proportion data (p) given by x/n where x is the number of occurrences and n is its number of opportunities.p-chartEmbedded ImageEmbedded Image
Count data (u) with n observations each in a known “area of opportunity” niu-chartEmbedded ImageEmbedded Image
Count data (c) with n observations each with a constant “area of opportunity”c-chartEmbedded ImageEmbedded Image