A company making tires for bikes is concerned about the exact width of its cyclocross tires. The company has a lower specification limit of 22.7 millimeters and an upper specification limit of 23.2 millimeters. The standard deviation is 0.13 millimeters and the mean is 22.9 millimeters.

What is the process capability index for the process?

Note: Round your answer to 4 decimal places.