**ASSIGNMENT #3:** *Variables Control Charts and Process Capability*

*INSTRUCTIONS: Use MINITAB 17 to complete the following exercises. You will need to read the data set description using the HELP command in order to have all the information needed to perform the analyses and make meaningful interpretations. Please submit your completed assignment, showing all relevant MINITAB output and comments, as ONE WORD document by the due date. This assignment is worth a total of 60 points.*

**[15 pts] **1. Use the data file **ACCOUNTS.MTW **in the Student8Datafolder and construct an

x-bar and r chart. Use all tests to determine whether the process is in statistical control. Assume assignable causes for out-of-control points. Find revised centerline and control limits by eliminating these points. Only include the output for the final control chart but discuss how you arrive at it in your comments. *Hint: use data options feature and select “leave gaps for excluded points.”*

**[15 pts] **2. Use the data file **FLEX2.MTW **in the Student8Datafolder to construct an x-bar and s chart for diameters of copper plated wires (data in C1). Use all tests to determine whether the process is in statistical control. Assume assignable causes for any out-of- control points. Find revised centerline and control limits by eliminating these points. Only include the output for the final control chart but discuss how you arrive at it in your comments. *Hint: use data options feature and select “leave gaps for excluded points.”*

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**[15 pts]** 3. Use the data file **LIGHTBULB.MTW** to perform capability analysis. Use specification

limits of 1250 ± 200 hours and assume a subgroup size of 5. Use an x-bar and r chart to see if the process is stable. Check to see if assuming normality is reasonable (use Kolmogorov-Smirnov). Include output for the control chart, the normality test, and process capability. Comment on the results.

** [15 pts]** 4. Use the data file **PIPESAMPLE.MTW** to perform capability analysis. Use a sample

size of 4 and specification limits 0.20 ± .10 (ignore the specifications in the data set description). Use an x-bar and r chart to see if the process is stable. Check to see if assuming normality is reasonable (use Kolmogorov-Smirnov). Include output for the control chart, the normality test, and process capability. Comment on the results.

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