Today, you took 10 samples of 20 units each. The first nine samples each had one defect. The last sample had zero defects. What can you conclude?
a) the process is out of control
b) the process is in a state of control
c) the last sample should be ignored because it was "too good"
d) you calculated the limits incorrectly because the LCL must be either negative or 0
e) the sample size must be increased
Answer: a