Options - Parameters
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Charts  P, Laney P', NP, G

You can enter historical data for estimating p. For example, if you have a known process parameter or an estimate obtained from past data, enter the value(s). If you do not specify a value for p, Minitab estimates it from the data. You can omit or include certain subgroups when estimating parameters using Estimate.

By default, Minitab estimates the process proportion defective, p, from the overall sample proportion. Then, Minitab calculates the center line and control limits using this value.

Dialog box item

Proportion: Enter the historical proportions as constants. If you enter one constant, all stages use that value; otherwise, enter a value for each historical group.