Introduction

The Shewhart control chart is a graphical and analytical tool for deciding whether a process is in a state of statistical control. You can use the SHEWHART procedure to display many different types of control charts, including all commonly used charts for variables and attributes. In addition, you can use the SHEWHART procedure to

• create charts from either raw data (actual measurements) or summarized data

• analyze multiple process variables

• specify control limits in terms of a multiple of the standard error of the plotted summary statistic or as probability limits

• adjust control limits to compensate for unequal subgroup sizes

• estimate control limits from the data, compute control limits from specified values for population parameters (known standards), or read limits from an input data set

• create historical control charts that display distinct sets of control limits for multiple time phases

• perform tests for special causes based on runs patterns (Western Electric rules)

• estimate the process standard deviation using various methods (variable charts only)

• accept numeric-valued or character-valued subgroup variables

• display subgroups with date and time formats

• save chart statistics and control limits in output data sets

• tabulate chart statistics and control limits

• produce charts as traditional graphics, ODS Graphics output, or legacy line printer charts. Line printer charts can use special formatting characters that improve the appearance of the chart. Traditional graphics can be annotated, saved, and replayed.