Scenario: Suppose you joined a start-up company to produce paper helicopters which are intended to be an educational toy. The name of the company is California Choppers. The company consists of 5 people (Peter, Meir, Jennifer, Sara, and Selina) who were responsible for the product development, and who are now responsible for production.
Each of the 5 production personnel works for an 8-hour shift with a production output of 20 helicopters. Each of them uses their own tools and measurement equipment, so they are concerned that the performance of helicopters produced on different shifts may vary.
Your role in the company is to provide expertise for quality assurance. As a first step, the team has asked you to institute an SPC process to understand performance variability of flight times when the helicopter is dropped from 5 feet.
The flight duration data was collected for one week (5 shifts) and is shown graphically as a Shewhart control chart. The data from shift 1 (samples 1 to 20) was used to set the control limits.
This data set appears to be under control, but upon close examination, it was found that there may be l process shifts from operator-to-operator. The data is provided on the next page.
Their team leader is convinced that they can control the production with a Shewhart control chart, but the rest of the team is not so sure. So they hired you as an SPC expert! Your first assignment is as follows:
- Explain why a Shewhart control chart is limited in its ability to detect smaller process shifts. You should use the data from the first five shifts to illustrate the points.
- Propose an alternate control chart approach, and explain why it’s an improvement.
- Graph the data using the alternative approach, showing the control limits.
Test-taking advice: This need not be a long document (max of 2 pages), but you need to be careful to articulate your ideas. I’d propose you format with an introductory paragraph, and then for each idea on why the Shewhart chart is limited- state the conjecture, and then explain why. Similarly, for the alternative approach, state your conjecture, and explain why it’s an improvement.
|Shift 1||Shift 2||Shift 3||Shift 4||Shift 5|