rules: Nelson's Quality Control Rules

Description Usage Arguments Rules list Source

Description

These rules are used for quality control (QC). Default values are set for Nelson's criteria, but they also support Westgard, AIAG, Montgomery and Healthcare QC rules.

Usage

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rule1(x, m = mean(x), s = sd(x))

rule2(x, m = mean(x), min.run = 9)

rule3(x, min.run = 6)

rule4(x, m = mean(x), min.run = 14, direction.mean = FALSE)

rule5(x, m = mean(x), s = sd(x), min.run = 3)

rule6(x, m = mean(x), s = sd(x), min.run = 5)

rule7(x, m = mean(x), s = sd(x), min.run = 15)

rule8(x, m = mean(x), s = sd(x), min.run = 8)

Arguments

x

vector with values

m

mean

s

standard deviation

min.run

minimal amount of sequential values before rule is triggered (defaults to Nelson's)

direction.mean

a logical to indicate whether n observations in a row must be tested for alternating in direction of the mean

Rules list

Nelson (N), Westgard (W), AIAG (A), Montgomery (M), Healthcare (H): N W A M H
--------------------------------------------------------------------------------------- ----- ----- ----- ----- -----
#1 One point is more than 3 standard deviations from the mean. 1 1 1 1 1
#2 n (or more) points in a row are on the same side of the mean 9 9 7 8 8
#3 n (or more) points in a row are continually incr. or decr. 6 - 6 6 6
#4 n (or more) points in a row alternate in direction, incr. then decr. 14 - 14 14 -
#5 n - 1 out of n points in a row are >2 sd from the mean 3 3 3 3 3
#6 n - 1 out of n points in a row are >1 sd from the mean 5 5 5 5 -
#7 >= n points in a row are within 1 sd of the mean 15 - 15 15 15
#8 >= n points in a row outside 1 sd of the mean, in both directions 8 - 8 8 -

Source

Nelson LS. The Shewhart Control Chart—Tests for Special Causes. Journal of Quality Technology [Internet]. Informa UK Limited; 1984 Oct;16(4):237–9. Available from: http://dx.doi.org/10.1080/00224065.1984.11978921


msberends/nelson documentation built on May 14, 2019, 7:21 p.m.