Aspen Plastics produces plastic bottles to customer order. The quality inspector randomly selects four bottles from the bottle machine and measures the outside diameter of the bottle neck, a critical quality dimension that determines whether the bottle cap will fit properly. The dimensions (in.) from the last six samples are

Bottle Sample 1 2 3 4 1 0.622 0.572 0.571 0.603 2 0.622 0.612 0.607 0.580 3 0.602 0.604 0.608 0.625 4 0.611 0.624 0.617 0.625 5 0.601 0.595 0.596 0.585 6 0.576 0.613 0.579 0.601

Suppose that the specification for the bottle neck diameter is 0.6000.050 in. and the population standard deviation is 0.013 in.

a. What is the process capability index?

The Cpk is ___ (Enter your response rounded to two decimal places.)