Flow Chart Analysis of Non-Normal Data

 

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Flowchart

When the retrieval setting for Force distribution is set to Automatic (the default), GainSeeker follows these steps to determine the data distribution and method for statistical calculations:

Uniform distribution and Non-Normal distribution (modeled)

  • Cp =

High Spec − Low Spec

d(U) − d(L)

  • CR =

d(U) − d(L)

High Spec − Low Spec

Mean + 3SD  is the point on the x-axis where 0.135% of the data is above the value

Mean − 3SD  is the point on the x-axis where 0.135% of the data is below the value

Mean + 4SD  is the point on the x-axis where 0.003% of the data is above the value

Mean − 4SD  is the point on the x-axis where 0.003% of the data is below the value

Six SD  = (Mean + 3SD) − (Mean − 3SD)

Median method for calculating Cpk

The calculations for d(U) and d(L) are described above.

Zu =

High Spec − Median

d(U) − Median

✕ 3
Zl =

Median − Low Spec

Median − d(L)

✕ 3
Cpk = Minimum of

Zu

3

or

Zl

3

Probability method for calculating Cpk

Zu = z value (from the normal distribution table) corresponding to the predicted percent above the high spec

Zl = z value (from the normal distribution table) corresponding to the predicted percent below the low spec

Cpk = Minimum of

Zu

3

or

Zl

3

Non-Normal (not modeled)

  • Zu =

High Spec − Median

High Value − Median

✕ 3
  • Zl =

Median − Low Spec

Median − Low Value

✕ 3
  • Cpk = Minimum of

Zu

3

or

Zl

3

  • Cp =

High Spec − Low Spec

High Value − Low Value

  • CR =

High Value − Low Value

High Spec − Low Spec

Mean + 3SD = Mean + (3 ✕ SD)

Mean − 3SD = Mean − (3 ✕ SD)

Mean + 4SD = Mean + (4 ✕ SD)

Mean − 4SD = Mean − (4 ✕ SD)

Six SD = 6 ✕ SD