The producer of electronic circuits in problem 4 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 only five circuits. The past average voltage for samples of size 5 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 this variables control chart versus the control chart described in problem 4. Which do you prefer?

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Sample 1 4 X 3.6 3.3 2.6 3.9 3.4 2.0 2.6 0.7 2. 2.3