top of page

Control Charts for Attributes

An attribute control charts plot nonconformities (defects) or nonconforming units (defectives). Where the nonconformity refers to a quality characteristic and a nonconforming unit refers to the overall product. Values are then classified into one of two categories, pass or fail. There are two types of charts used when plotting the nonconforming units, the P chart and the NP chart. The P chart shows the portion or fraction of the nonconforming units on the y-axis. While the NP chart shows the whole number of nonconforming units on the y-axis. Then there is a C chart which is a control chart that deals with the number of nonconformities. 

bottom of page