X Bar and R Chart VS. P-Chart Choosing the Right Approach For each scenario below, decide whether the X bar and R chart, OR the p-chart would be the correct approach for the purposes of SPC. Remember, X bar and r charts are used when we are MEASURING a value that represents some dimension of quality. P charts are used when the quality check is a "pass/fail" assessment of a particular attribute. 1) General Motors is examining the paint finish on its finished vehicles, looking for surface imperfections. X bar and R chart b. P-chart a. 2) A college administrator is examining the success of students in particular programs using samples of student GPA's. X bar and R chart b. P-chart a. 3) A college administrator is examining the success of samples of students in particular programs. Sample data is collected regarding the number of students who are granted the credit versus those that are not. a. X bar and R chart b. P-chart 4) Coca-Cola is examining the results of its filling line. Sample data is collected regarding the volume of product in each bottle. a. X bar and R chart b. P-chart 5) Frito-Lay is interested in the sealing process for its bags of chips. Data is collected to record whether bags are or are not appropriately sealed on the top and side seams of the packaging bag. a. X bar and R chart b. P-chart 6) A manufacturer is interested in the length of a particular part. Sample data is collected to record the length in centimetres. a. X bar and R chart b. P-chart 7) A manufacturer is interested in the length of a particular part. Sample parts are put into a fixture and a record is made of whether they do fit or don't fit into the fixture. a. X bar and R chart b. P-chart