Calculate Capability Indices with Only One Specification USL, upper specification limit; LSL, lower specification limit *Estimated sigma = average range d2 Common understanding includes the fact that Cpk climbs as a process improves – the higher the Cpk, the better the product or process Using the formula above, it’s easy to calculate Cpk once the mean, standard deviation, and upper and lower specification limits are known Only One
Cpk vs. Sigma Level: What’s the Difference? - isixsigma. com Cpk = min (USL-mean 3σ, mean-LSL 3σ) This means that Cpk is equal to the minimum value of these two calculations For example, if USL-mean 3σ gives you 1 16 and mean-LSL 3σ gives you 1 25, your Cpk is going to be 1 16 That is because 1 16 is the lower of the two amounts and is therefore used as the minimum value
A Guide to Control Charts - iSixSigma How do you know which control charts to use for an improvement project? Our guide can help you identify which works best for your needs
Cp, Cpk, Pp and Ppk: Know How and When to Use Them These represent categorical variables, which by definition carry an ideal USL of 100 percent error-free processing, rendering the traditional statistical measures (Cp, Cpk, Pp, and Ppk) inapplicable to categorical variables
Process Capability Calculations with Non-Normal Data Data that is not distributed normally can be analyzed more effectively by: 1) dividing data into subsets according to business subprocesses, 2) mathematically transforming data and specification limits and 3) turning continuous data into discrete data
Getting the Most out of a Capability Analysis - iSixSigma Many articles describe the difference between the process capability indices simply: one is short term, one is long term Moving beyond such a description, this article focuses on the untapped power of capability analysis and shows you how to use them to your advantage