Quantitative Analysis for Management, 13/e

15.4 Control Charts for Attributes

Control charts for $\overline{x}$ and R do not apply when we are sampling attributes, which are typically classified as defective or nondefective. Measuring defectives involves counting them (e.g., number of bad lightbulbs in a given lot or number of letters or data entry records typed with errors). There are two kinds of attribute control charts: (1) those that measure the percent defective in a sample, called p-charts, and (2) those that count the number of defects, called c-charts.

Sampling attributes differ from sampling variables.

p-Charts

p-charts are the principal means of controlling attributes. Although attributes that are either good or bad follow the binomial distribution, the normal distribution can be used ...