d. Other Chart Types
1) P charts show the percentage of defects in a sample. They are based on an attribute (acceptable/ not acceptable) rather than a measure of a variable.
2) C charts also are attribute control charts. They show defects per item.
3) An R chart shows the range of dispersion of a variable, such as size or weight. The center line is the overall mean.
4) An x-bar chart shows the sample mean for a variable. The center line is the average range.