Additional Algo $9-1$ Process Capability Index

A milling process has an upper specification of $2\mathrm{.}058$ millimeters and a lower specification of $1\mathrm{.}921$ millimeters. A sample of parts had a mean of $1\mathrm{.}96$ millimeters with a standard deviaiton of $0\mathrm{.}014$ millimeters.

What is the process capability index for this system?

Note: Round your answer to $4$ decimal places.

Capability index