Rejection Calculator

Customers and manufacturers use different methods to specify the quality required. Some of the methods used are percentage variation, Cp, Cpk, Z, percentage rejection, ppm rejection, ppb rejection, etc.

This app helps to decide if the actual data is within the specifications or not.

You have to enter at least one out of Lower Specification Limit (LSL) and Upper Specification Limit (USL). Then you have to enter the desired Cpk. If the end user / customer has specified the Z value, then you can just divide it by 3 and enter in the Cpk box.

Next, you enter the Actual Average and Actual Standard Deviation.

The app then calculates the actual Cp, the actual Cpk and the actual Z values.

Quite often, users are satisfied with this much information. However, for those who need this to be 'interpreted', the app also comments on the 'effect' of all the calculated figures. So, maybe the process is already well in control, or the variation is too high or the center needs to be shifted.

Another useful 'interpretation' is the estimated rejection levels. You come to know the estimated 'under size' and 'over size' rejection expressed as percentage and parts per million (ppm).