Assume a process follows normal distribution, and that the control limits are within specification limits for all three choices below. Assume all outcomes outside the control limits are discarded as poor quality, even if some of the discarded outcomes are within specification limits. The cost of poor quality is highest when:
a. Control limits are within 3σ on either side of the mean.
b. Control limits are within 2σ on either side of the mean.
c. Control limits are within 1σ on either side of the mean.