Question

A metal fabricator produces connecting rods with an outer diameter that has a 1 ± 0.01 inch specification. A machine operator takes several sample measurements over time and determines the sample mean outer diameter to be 1.003 inches with a standard deviation of 0.002 inches.
Calculate the process capability index for this example.

Answer 1

Answer:

0.25

Explanation:

Process Capability measures the efficiency of a process

It is given by this equation

Cp = (USL-LSL)/6σ

Where USL is the upper Specification Limit = 1.003

and LSL is the Lower Specification Limit = 1 inch

σ is the standard deviation = 0.002 inches

Therefore

Cp = (1.003 - 1)/6 × 0.002

=0.003/0.012

Cp = 0.25