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SCHART Statement |

The SCHART statement creates an *s* chart
for subgroup standard deviations, which is
used to analyze the variability of a process.^{*}

You can use options in the SCHART statement to

- compute control limits from the data based on a multiple of the standard error of the plotted standard deviations or as probability limits
- tabulate subgroup sample sizes, subgroup standard deviations, control limits, and other information
- save control limits in an output data set
- save subgroup sample sizes, subgroup means, and subgroup standard deviations in an output data set
- read preestablished control limits from a data set
- specify a method for estimating the process standard deviation
- specify a known (standard) process standard deviation for computing control limits
- display distinct sets of control limits for data from successive time phases
- add block legends and symbol markers to reveal stratification in process data
- superimpose stars at points to represent related multivariate factors
- clip extreme points to make the chart more readable
- display vertical and horizontal reference lines
- control axis values and labels
- control layout and appearance of the chart

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