Question

5.11.

A manufacturing process produces 500 parts per hour. A sample part is selected about every half hour, and after five parts are obtained, the average of these five measurements is plotted on an x control chart.

(a) Is this an appropriate sampling scheme if the assignable cause in the process results in an instantaneous upward shift in the mean that is of very short duration?

(b) If your answer is no, propose an alternative procedure. If your answer is yes, justify.

5.12.

Consider the sampling scheme proposed in Exercise 5.11. Is this scheme appropriate if the assignable cause results in a slow, prolonged upward drift in the mean? If your answer is no, propose an alternative procedure.

I know the answer to 5.11, but what about 5.12?

Answer 1

(a)

This isn't a proper testing plan for the given situation, since each datum point

recorded for the variable is for a base time of a 30(5)=150 minutes or 2.5 hours.

In the event that it gives some spike change for around brief periods, the spike isn't really

sensible.

b)

The issue is that the procedure may move to a wild state and back to an in-

control state in under 30 minutes. In this way, an elective inspecting technique is

every subgroup ought to be an irregular example of all parts delivered in the last 2

hours.