Reliability Analysis - Predictions, Testing and StandardsĪnalysis variation among the lots during cpk calculation. Tolerance definition based on expected Cp/cpk Inspection, Prints (Drawings), Testing, Sampling and Related TopicsĬp and Cpk for straightness and parallelism LTPD, AQL, Ppk and Cpk validation sampling plan table What's the difference between 1.32 and 1.33 Cpk? Is it possible to determine the Cpk value from Cp and Cr values?Ĭpk value interpretation - What is the significance of Cpk value of 1.33?Ĭalculating Defect Rate (PPM) from a Cpk valueĬpk: Indispensible Index or Misleading MeasureĬan I use Cpk to compare if one part is usable in another part?Ĭapability in sewing processes CP,CPk,PP,PPk Spc Question - When the Cpk value is bigger than 2.0Īttribute capability indices - Cpk and/or Ppk value for an attribute type of feature Is it possible to get a negative Cpk value? What is the value of Cpk for a new process? Ppk/Cpk value with 1-sided specification - Only given a lower specification Which standard Cpk value intervals are common or frequently used?Īny 'Rule of Thumb' for Acceptable Cpk Value - Injection Molding?Ĭan Ppk value be greater than Cpk and if yes, under what conditions? Methods used to calculate Cpk value - Need help for Cpk Calculation How is Cpk /Ppk value calculated in Minitab since I have subgroup size of 1 How to validate Microsoft Excel Spreadsheet Calculations for the Cpk valueĬapability, Accuracy and Stability - Processes, Machines, etc.Ĭpk for Hardness - PPAP rejected due to no Cpk value being given for a hardness Based on the Minitab output above, we could. Value of Ppk or Cpk when targeting thinner material A statement of whether there were statistically significant differences between your two related groups, including the relevant median difference (Estimated Median), Wilcoxon signed-rank test statistic, W (Wilcoxon Statistic), and significance level, or more specifically, the 2-tailed p-value (P). Statistical Analysis Tools, Techniques and SPC

If you find that the process is indeed stable and the measurement system is adequate, then I might consider transforming the data though I prefer using a non normal capability analysis if a rational non normal distribution is appropriate. In your situation, I would evaluate the process over a longer time period to determine whether it was truly stable, and would evaluate the measurement system to determine whether improvements were warranted. The focus should be on stabilizing the process or bringing the process streams closer together. In cases such as that, it is wrong to transform the data. In almost every case, the data were non normal because the process was unstable or was a mixture of multiple process streams.

In my role as a Master Black Belt, I see a lot of Black Belts transforming non normal data without understanding why it is non normal. The biggest reason is that you will lose a lot of information contained in the data. I am always reluctant to transform data for a number of reasons.

P value minitab