Rules for Shewhart charts

Function which implements rules to signal out of control points in Shewhart charts.

Usage

qccRules(object, rules = object$rules)

Arguments

object

an object of class 'qcc'.

rules

a vector of values specifying the rules used to declare a process out-of-control. Possible values are:

1.

One point plots outside 3-sigma control limits.

2.

Two of three consecutive points plot beyond a 2-sigma limit.

3.

Four of five consecutive points plot beyond a 1-sigma limit.

4.

Eight consecutive points plot on one side of the center line.

These are often known as Western Electric rules.

Value

The function returns a vector of the same length as the statistics charted with value NA if no rule is violated, and numerical values corresponding to the violated rule. If more than one rule is violated, the value returned corresponds to the most serious violation.

Author

Luca Scrucca