Calculation Discrepancy about Capability Analysis for non-normal distribution

Adam_Xu

Hello,

 

I tried to use percentile function to calculate Capability Index for Non-normal distribution by following JMP's guide as below:

However, when I input those formula in Excel and found discrepancies for Cp/Cpl/Cpu/CpK/Cpm results compared with JMP output:

I wonder to know what's the issue? Is JMP used different formula for those calculation?

Thank you very much!

Capability Analysis with Non Normal Distribution Data (Example).jmp

Adam_Xu

I addressed this issue. The calculation could not using percentile function directly. The right calculation should be finding the best fitted distribution and then use relevant distribution Quantile function instead. Thanks