Z Benchmark Potential

  1. Where

ZLSL = Z benchmark LSL
LSL = Lower Specification Limit
= Sample mean
swithin = Sigma within estimate
  1. Where

ZUSL = Z benchmark LSL
USL = Upper Specification Limit
= Sample mean
swithin = Sigma within estimate
  1. Where

ZPotential = Z benchmark Potential
ZLSL = Z benchmark Lower Specification Limit
ZUSL = Z benchmark Upper Specification Limit
Φ-1 = Inverse Standard Normal distribution function
Φ = Cumulative Standard Normal distribution function
  1. Where

df1 = Numerator degrees of freedom for F distribution
N = Total number of observations
Φ = Cumulative Standard Normal distribution function
ZLSL = Z benchmark Lower Specification Limit
ZUSL = Z benchmark Upper Specification Limit
  1. Where

df2 = Denominator degrees of freedom for F distribution
N = Total number of observations
Φ = Cumulative Standard Normal distribution function
ZLSL = Z benchmark Lower Specification Limit
ZUSL = Z benchmark Upper Specification Limit
  1. Where

ZLowerCI = Z benchmark Lower CI
Φ-1 = Inverse Standard Normal distribution function
= Value from F(df1,df2) distribution with area of α in right tail
  1. Where

df1 = Numerator degrees of freedom for F distribution
N = Total number of observations
Φ = Cumulative Standard Normal distribution function
ZLSL = Z benchmark Lower Specification Limit
ZUSL = Z benchmark Upper Specification Limit
  1. Where

df2 = Denominator degrees of freedom for F distribution
N = Total number of observations
Φ = Cumulative Standard Normal distribution function
ZLSL = Z benchmark Lower Specification Limit
ZUSL = Z benchmark Upper Specification Limit
  1. Where

ZUpperCI = Z benchmark Upper CI
Φ-1 = Inverse Standard Normal distribution function
= Value from F(df1,df2) distribution with area of α in right tail

Table for Function(n)

n Function(n)
Using Ranges:
All n
  1. 9
Using Sample Standard Deviation:
2
  1. 88
3
  1. 92
4
  1. 94
5
  1. 95
6-7
  1. 96
8-9
  1. 97
10-17
  1. 98
18-64
  1. 99
>64 1

 10.

Where

Function(n) = Value from table above
n = Average sample size
k = Number of samples
  1.  

    Where

Cp LowerCI = Cp Lower CI
Cp = Potential Capability
χ2 (α,df) = Value from χ2 (df) distribution with area of α in right tail
  1.  

    Where

Cp UpperCI = Cp Upper CI
Cp = Potential Capability
χ2 (α,df) = Value from χ2 (df) distribution with area of α in right tail
  1. Where

Cpk LowerCI = Cpk Lower CI
Cpk = Demonstrated Excellence
Φ-1 = Inverse Standard Normal distribution function
k = Number of samples
n = Average sample size

 14.

Where

Cpk UpperCI = Cpk Upper CI
Cpk = Demonstrated Excellence
Φ-1 = Inverse Standard Normal distribution function
k = Number of samples
n = Average sample size
  1. Where

PPM<LSL = Parts per million less than LSL
Φ = Cumulative Standard Normal distribution function
ZLSL = Z benchmark Lower Specification Limit
  1. Where

PPM>USL = Parts per million less greater than USL
Φ = Cumulative Standard Normal distribution function
ZUSL = Z benchmark Upper Specification Limit
  1. Where PPMTotal = Total Parts per million

Observed Process Performance:

  1. Where

PPM<LSL = Parts per million less than LSL
LSL = Lower Specification Limit
N = Total number of observations
  1. Where

PPM>USL = Parts per million greater than USL
USL = Upper Specification Limit
N = Total number of observations
  1. Where PPMTotal = Total Parts per million

  2. Where

= Sample mean
soverall = Estimate of overall sigma
  1. Where

df = Degrees of freedom for χ2 distribution
k = Number of samples
n = Average sample size
  1. Where

Cpm LowerCI = Cpm Lower CI
Cpm = Potential Capability II
χ2 (α,df) = Value from χ2 (df) distribution with area of α in right tail
  1. Where

Cpm UpperCI = Cpm Upper CI
Cpm = Potential Capability II
χ2 (α,df) = Value from χ2 (df) distribution with area of α in right tail

Computation for Z Benchmark overall:

  1. Where

ZLSL = Z benchmark LSL
LSL = Lower Specification Limit
= Sample mean
soverall = Sigma overall estimate
  1. Where

ZUSL = Z benchmark USL
USL = Upper Specification Limit
= Sample mean
soverall = Sigma overall estimate
  1. Where

ZOverall = Z benchmark Overall
ZLSL = Z benchmark Lower Specification Limit
ZUSL = Z benchmark Upper Specification Limit
Φ-1 = Inverse Standard Normal distribution function
Φ = Cumulative Standard Normal distribution function
  1. Where

df1 = Numerator degrees of freedom for F distribution
N = Total number of observations
Φ = Cumulative Standard Normal distribution function
ZLSL = Z benchmark Lower Specification Limit
ZUSL = Z benchmark Upper Specification Limit
  1.   Where

df2 = Denominator degrees of freedom for F distribution
N = Total number of observations
Φ = Cumulative Standard Normal distribution function
ZLSL = Z benchmark Lower Specification Limit
ZUSL = Z benchmark Upper Specification Limit
  1. Where

ZLowerCI = Z benchmark Lower CI
Φ-1 = Inverse Standard Normal distribution function
= Value from F(df1,df2) distribution with area of α in right tail
  1. Where

df1 = Numerator degrees of freedom for F distribution
N = Total number of observations
Φ = Cumulative Standard Normal distribution function
ZLSL = Z benchmark Lower Specification Limit
ZUSL = Z benchmark Upper Specification Limit
  1. Where

df2 = Denominator degrees of freedom for F distribution
N = Total number of observations
Φ = Cumulative Standard Normal distribution function
ZLSL = Z benchmark Lower Specification Limit
ZUSL = Z benchmark Upper Specification Limit
  1. Where

ZUpperCI = Z benchmark Upper CI
Φ-1 = Inverse Standard Normal distribution function
= Value from F(df1,df2) distribution with area of α in right tail
  1. Where

df = Degrees of freedom for χ2 distribution
k = Number of samples
n = Average sample size
  1. Where

P p LowerCI = Pp Lower CI
Pp = Performance Index
χ2 (α,df) = Value from χ2 (df) distribution with area of α in right tail

 36.

Where

P p UpperCI = Pp Upper CI
Pp = Performance Index
χ2 (α,df) = Value from χ2 (df) distribution with area of α in right tail
  1. Where

Ppk LowerCI = Ppk Lower CI
Ppk = Performance Demonstrated Excellence
Φ-1 = Inverse Standard Normal distribution function
k = Number of samples
n = Average sample size
  1. Where

Ppk UpperCI = Ppk Upper CI
Ppk = Performance Demonstrated Excellence
Φ-1 = Inverse Standard Normal distribution function
k = Number of samples
n = Average sample size

Potential Process Performance:

  1. Where

PPM<LSL = Parts per million less than LSL
Φ = Cumulative Standard Normal distribution function
ZLSL = Z benchmark Lower Specification Limit
  1. Where

PPM>LSL = Parts per million greater than LSL
Φ = Cumulative Standard Normal distribution function
ZUSL = Z benchmark Upper Specification Limit
  1. Where PPMTotal = Total Parts per million