SKEDSOFT

Process Capability Indices

Calculating the Process Mean (Xbar)

Where n is the sample size and Xi is the data value.

Calculate the Process Spread (Standard Deviation, s)

To obtain an accurate estimate of the process spread (standard deviation); at least 60 data points are needed. If less than 60 data points are available, use  the following formula with the error correction factors given in Table 1.