Question: The producer of electronic circuits in problem has reconsidered the method of quality control and has decided to use process control by variables instead of attributes. For variables control, a circuit voltage will be measured using a sample of five circuits. The past average voltage for samples of 5 units has been 3.4 volts, and the range has been 1.3 volts.
a. What would the upper and lower control limits be for the resulting control charts (average and range)?
b. Five samples of voltage are taken with the following results:
What action should be taken, if any?
c. Discuss the pros and cons of using the variables control charts versus the control chart described in problem. Which do you prefer?
Problem: A process for producing electronic circuits has achieved very high yield levels. An average of only 8 defective parts per million is currently produced.
a. What are the upper and lower control limits for a sample size of 100?
b. Recompute the upper and lower control limits for a sample size of 10,000.
c. Which of these two sample sizes would you recommend? Explain.