Select all statements that are true about process capability ratios:
a) used to find the proportion of individual outputs(products) that would be accepted by the customer (designer)- fall within specifications
b) calculated using customer (designer) specification and the process STD
c) specifications are determined externally by the customer (designer)
d) uses control-limits which are calculated using process properties- eg mean and std
e) applied to verify a process is stable-in-control
f) samples statistics ( eg average, percentage) are compared to control limit