An attribute chart is a type of control chart for measuring attribute data (vs. continuous data). There are four types of attribute charts: c chart, n chart, np chart, and u chart. The choice of charts depends on whether you have a problem with defects or defectives, and whether you have a fixed or varying sample size.
Use: The attribute chart is useful in monitoring for assignable-cause variation in defects and defectives. Note that whenever you are monitoring attribute data, you are really counting dead bodies. It’s too late. There’s already a defect. It’s too late. There’s already a defective. Isn’t it better to look upstream in the process so that you can prevent a dead body? That’s why one should always strive to look upstream for continuous data because that’s where improvements and preventions occur. Try to minimize your use of attribute charts. Note: There is a matrix in the reading materials that will show you which chart to use for four different conditions (i.e., defects with a varying sample size, defects with a constant sample size, defectives with a varying sample size, and defectives with a constant sample size.
