Control Charts for AttributesTwo ch

Control Charts for AttributesTwo charts commonly used for performance measures based on attributes measures are the p- and c-chart. The p-chart is used for controlling the proportion of defects generated by the process. The c-chart is used for controlling the number of defects when more than one defect can be present in a service or product.p-Charts The p-chart is a commonly used control chart for attributes. The performance characteristic is counted rather than measured, and the entire service or item can be declared good or defective. For example, in the banking industry, the attributes counted might be the number of nonendorsed deposits or the number of incorrect financial statements sent to customers. The method involves selecting a random sample, inspecting each item in it, and calculating the sample proportion defective, p, which is the number of defective units divided by the sample size.Sampling for a p-chart involves a “yes or no” decision: The process output either is or is not defective. The underlying statistical distribution is based on the binomial distribution. However, for large sample sizes, the normal distribution provides a good approximation to it. The standard deviation of the distribution of proportion defectives,