HELPFUL NOTATION


Symbol

Description

A 2

Multiplier of for calculating -chart control limits

2

Multiplier of for calculating -chart control limits

A 3

Multiplier of for calculating X -chart control limits

B 3

Multiplier of to determine s -chart LCL

B 4

Multiplier of to determine s -chart UCL

C

Number of nonconformities or defects in a specified inspection unit (sample size )

C 4

Factor for estimating ƒ x from

ƒ 2

Factor for estimating ƒ x from

Factor for estimating ƒ x from

D

Weighted number of defects (demerits)

D 3

Multiplier of R to determine R -chart LCL

Multiplier of to determine R -chart LCL

D 4

Multiplier of to determine R -chart UCL

E 2

Multiplier of m for calculating X -chart control limits

k

Number of subgroups or samples

LCL

Lower control limit

LSL

Lower specification limit

¼

True population average "mu"

n

Sample size: number of items in sample

np

Number of nonconforming items or defectives in a sample size of n

p

Proportion or fraction of nonconforming items "fraction defective"

R

Range: X highest - X lowest

Average of sample ranges

Median of sample ranges

Rm

Moving range

m

Average of the moving range

S

Sample standard deviation

Average of sample standard deviations

ƒ x

Standard deviation of a frequency distribution of individual measurements [ X' s]

Standard deviation of a frequency distribution of sample averages [ 's]

ƒ '

True population standard deviation "sigma prime"

X

A random variable: an individual measurement

X i

The i th random variable or individual measurement

Sample averages: X 1 + X 2 + ... X n / n

The i th sample average

Average of the averages: "grand averages"

True population average: "X-bar prime" = ¼

Sample median

Median of the sample medians: "grand median"

u

Nonconformities or defects per production unit

U

Weighted number of defects per production unit

UCL

Upper control limit

USL

Upper specification limit

Z

Standardized normal variable = X - ¼ / ƒ x




Six Sigma and Beyond. Statistical Process Control (Vol. 4)
Six Sigma and Beyond: Statistical Process Control, Volume IV
ISBN: 1574443135
EAN: 2147483647
Year: 2003
Pages: 181
Authors: D.H. Stamatis

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