Parts Manufactured by an Injection Molding Process Are Subjected to a Compressive

Multiple Choice

Parts manufactured by an injection molding process are subjected to a compressive strength test.We wish to monitor the compressive strength of the parts manufactured by this process using both and s charts.Samples of size 9 are to be taken at regular intervals,and their mean compressive strength (in psi = pounds per square inch) and standard deviation are plotted on the charts in time order.The target values for the compressive strengths are a mean of  = 80 psi and a standard deviation of  = 3 psi.The control chart constants are (partially) reproduced below. Suppose at the time of sample 10,we observe a mean of 85 psi.What should we do?

A) Declare the process out of control.
B) Continue sampling-the process is still in control.
C) Continue sampling,but increase the sample size to 16.The process is barely in control.
D) Continue sampling,but reduce the sample size to 4.The process is well in control.