In industrial statistics, the p-chart is a type of control chart
that monitors the proportion of nonconforming units in a sample.
The appropriate data for p-charts are attribute data (conform or
non-conform, yes or no, etc.). The subgroup size should ideally be
equal, although unequal sample sizes can be accommodated. p-chart #
The "p" comes from use of the proportion of nonconforming items #
Need a good definition of nonconforming items - usually a
categorical definition # Can be of equal or unequal subgroups #
Normally need large subgroups - can even be up to total for the
period