TM 620 Fall 2008 Session Six Homework Solutions Some of these questions do not have a universal answer. Therefore, the answers are written to elicit a range of potential answers based on differing perspectives. When this is true, it is particularly important for the student to concentrate on justifying their selected perspective. Chapter Ten Discussion Questions 7. Describe the purpose of a Pareto chart. Describe an instance (other than the one in the book) in which a Pareto chart could be effectively used. A Pareto Chart is a histogram that allows the analyst to identify and prioritize potential or real problems based upon Juran’s “80/20” rule. There are many personal and professional examples you could select to describe. 9. What is the purpose of a cause-and-effect (Ishikawa) diagram? Often workers spend too much time focusing improvement efforts on the symptoms of problems rather than the causes. The Ishikawa cause and effect diagram is a good tool to help move to lower levels of abstraction in solving problems. The diagram looks like the skeleton of a fish: the problem being the head of the fish, major causes being the "ribs" of the fish, and sub-causes forming smaller "bones" off of the ribs. Figure 10-5 in the text shows an Ishikawa diagram that was performed for a wood mill that was experiencing problems with wobbling blades in its saws. The symptom of the problem was the wobbly blade. The major causes were associated with machines, materials, people and methods. Under people, it was found that workers were not properly trained. Under machines, it was found that the blade was being setup off-center. 10. Describe the purpose of a check sheet. Describe an instance (other than the ones in the book) in which a check sheet could be effectively used. A check sheet is a simple mechanism that is used to gather information that can be used to diagnose a problem. On page 303, the text uses the check sheet to collect information that will be used to compile a histogram. 13. What is the purpose of a control chart? A control chart provides information about a product or service that have measurable quantities. This information can be used to detect changes in the system. 15. What is the purpose of an affinity diagram? An affinity tool is a brainstorming technique that will allow the team to take an issue, break it down to component sub-issues, and enable the team to isolate the root problems and provide solutions to them. 20. What is the purpose of a process decision program chart? A process decision program chart is used to help brainstorm possible contingencies or problems associated with the implementation of some program or improvement. The tool can take the form of either an outline or a tree chart. Chapter Ten Problems 7. Develop a histogram for the data given in the book. Develop two separate histograms for hours of overtime and days absent. How do the data appear to be distributed? Historgram 14 12 Frequency 10 8 6 4 2 0 0-99 100-199 200-299 300-399 400-499 3 4+ Hours of Overtime Histogram 8 7 Frequency 6 5 4 3 2 1 0 0 1 2 Days Absent Hours of overtime appears to be fairly normal with a small skew. Days absent appears to be fairly uniform. 8. Using the data in Problem 7, develop a scatter plot of hours of overtime versus days absent. Do the data overtime hours and days absent appear to be correlated? Scatter Plot 7 6 Days Absent 5 4 3 2 1 0 0 50 100 150 200 250 300 350 400 450 500 Hours of Overtime Yes, days absent and hours of overtime do appear to be correlated. 13. For the data in the book, develop a Pareto analysis. The letters A, B, C, D, E, and F are problems that occur in a process. Which cause should you focus on first? Pareto Chart 25 Frequency 20 15 10 5 0 A B C D E F Problem Type We should focus on A first. 26. Complete the analysis for the prioritization matrix information be finding the final ranking. Decision Alt.s Machine 1 Machine 2 Machine 3 Machine 4 Criterion A 0.3 1 2 3 4 Criterion B 0.2 3 2 4 1 Criterion C 0.5 4 2 1 3 Scores 2.9 2 2.2 2.9 Final Ranking 3 1 2 3