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. What is the center line for the s chart?

A) 0.7 psi
B) 2.9 psi
C) 3 psi
D) 5.1 psi