- When to use the S chart
- Use the S chart when your subgroup sizes are 9 or greater. S charts use all the data to calculate the subgroup process standard deviations. You should consider using S charts for processes with a high rate of production or when data collection is quick and inexpensive.
- When to use the R chart
- Use the R chart when your subgroup sizes are 8 or less.
The maximum subgroup size in Minitab's R chart is 100.