A process that is considered to be in control measures an ingredient in ounces. Below are the last 10 samples (each of size n = 5) taken. The population standard deviation is 1.36.

SAMPLES

1 2 3 4 5 6 7 8 9 10

10 9 13 10 12 10 10 13 8 10

9 9 9 10 10 10 11 10 8 12

10 11 10 11 9 8 10 8 12 9

9 11 10 10 11 12 8 10 12 8

12 10 9 10 10 9 9 8 9 12

a) What is the process standard deviation ?

b) If z = 3, what are the control limits for the mean chart?

c) What are the control limits for the range chart?

d) Is the process in control?