<P> In statistical quality control, the p - chart is a type of control chart used to monitor the proportion of nonconforming units in a sample, where the sample proportion nonconforming is defined as the ratio of the number of nonconforming units to the sample size, n . </P> <P> The p - chart only accommodates "pass" / "fail" - type inspection as determined by one or more go - no go gauges or tests, effectively applying the specifications to the data before they are plotted on the chart . Other types of control charts display the magnitude of the quality characteristic under study, making troubleshooting possible directly from those charts . </P> <P> The binomial distribution is the basis for the p - chart and requires the following assumptions: </P> <Ul> <Li> The probability of nonconformity p is the same for each unit; </Li> <Li> Each unit is independent of its predecessors or successors; </Li> <Li> The inspection procedure is same for each sample and is carried out consistently from sample to sample </Li> </Ul>

The underlying statistical distribution for the​ p-chart is the