14-1 Control Charts for Variation and Mean 711 Statistical Literacy and Critical Thinking 1. Run Charts and Control Charts a. What is a run chart and what is its purpose? b. What is an R chart and what is its purpose? c. What is an x chart and what is its purpose? 2. Control Limits In a control chart, what are upper and lower control limits, and what is their purpose? 3. Statistically Stable Process What does it mean to have a statistically stable process? 4. Lake Mead Water Elevations Many people in Nevada, Arizona, and California get water and electricity from Lake Mead and Hoover Dam. Shown below are an x chart (top) and an R chart (bottom) obtained by using the monthly water elevations (ft) of Lake Mead at Hoover Dam (based on data from the U.S. Department of the Interior). The control charts are based on the 12 monthly water elevations for each of 83 consecutive and recent years. What do these control charts tell us about Lake Mead? Pepsi Cans. In Exercises 5–8, refer to the axial loads (pounds) of aluminum Pepsi cans that are 0.0109 in. thick, as listed in Data Set 41 “Aluminum Cans” in Appendix B. An axial load of a can is the maximum weight supported by the side, and it is important to have an axial load high enough so that the can isn’t crushed when the top lid is pressed onto the top. There are seven measurements from each of 25 days of production. If the 175 axial loads are in one column, the first 7 are from the first day, the next 7 are from the second day, and so on, so that the “subgroup size” is 7. 5. Pepsi Cans: Notation After finding the sample mean and sample range for each of the 25 days, find the values of x and R. Also find the values of LCL and UCL for an R chart, then find the values of LCL and UCL for an x chart. 6. Pepsi Cans: Run Chart Treat the 175 axial loads as a string of consecutive measurements and construct a run chart. What does the result suggest? 7. Pepsi Cans: R Chart Treat the seven measurements from each day as a sample and construct an R chart. What does the result suggest? 8. Pepsi Cans: x Chart Treat the seven measurements from each day as a sample and construct an x chart. What does the result suggest? 14-1 Basic Skills and Concepts
RkJQdWJsaXNoZXIy NjM5ODQ=