21What is the LCL for the Xbar 22What is the LCL for the R c

21.What is the LCL for the X-bar?

22.What is the LCL for the R chart?

23.Both the X-bar and the R chart show that the process appears to be:

a. not in a state of statistical control

b. in a state of statistical control

c. very weak

d. efficient

e. inefficient

24.Assuming that the process standard deviation has remained at its historical value of .01, what is the UCL for the mean

25. the x-bar chart, under the assumption given in problem 24 shows that the process is:

a. not in a state of statistical control

b. in a state of statistical control

c. very weak

d. inefficient

e. none of the above

26. if the process is not in control, it is necessary to:

a. correct the common cause variation only

b. correct the special cause varition only

c. correct both common and special cause variation

d. do nothing

e. none of the above

Solution

21) Lower Control Limit (LCL) = X double bar - A2 * R bar=11.49965-0.577*0.04875=11.47152

22)

R cahrt

LCL=D3Rbar=0

23) all the xabr and R values are within the control limits. (this is verified by calculation). Hence the process is in a state of statistical control.

24) ucl=11.49965+0.577*0.01=11.5054

25) some points fall outside the control limits, hence not in a state of statistical control.

26) correct the special cause varition only