Brain Teasers: A Manager's Challenge: Investigating Cause

Anyone who has faced a production problem with a need to solve it by using production data can relate to the notion of a brain teaser. The brain teasers presented here are based on real-world situations encountered by workers in manufacturing environments. The brain teasers have three parts: (1) the situation, (2) available data or other supporting information and (3) questions that various workers need answered for continual improvement.


As engineering manager for a company that manufactures motorcycles, Jay is accountable for managing the engineering budget, which includes meeting the schedule for parts required by assembly and the overtime necessary if the schedule is not met. For the past three months, Jay has been over budget, parts have been sent to assembly late and overtime has increased.

In preparing for a meeting with his boss to discuss the situation, Jay discovered that all of the "bad news" in his measures happened within a month after the plant adopted a new just-in-time system of scheduling in May 2005. Jay wants to know if this new system could be related to the problems with the budget, schedule and overtime figures. He decides to ask the process improvement coordinator, Rachel, for help in analyzing the data collected specific to this issue.

Available data

Jay provided data for the past 15 months on the deviation from budget, compliance with schedule for parts and overtime hours. He then asked Rachel to analyze the data to see if the adoption of the just-in-time system could be the cause of the problems. The data are given in the table, "Budget, Schedule and Overtime Data for Engineering."


1. What analysis technique should Rachel use with Jay's data?

2. Is there evidence in these data of exceptional causes of variation?

3. How can Jay justify to his boss that the new just-in-time scheduling system is causing an increase in budget, or reducing the compliance to schedule or increasing the overtime hours worked?

4. Recommend a focus for Jay's meeting with his boss.

Answers to September Brain Teaser

When Patty, the production manager for a company that makes computer components and supplies, learns of a customer complaint about the width of tape for back-up tape drives, she asks for a comparison of the data analysis sent with shipment vs. the one from the customer. Patty's company shows that the production process for making the tape is predictable, while the customer's analysis shows an unpredictable process.

Q: Is the analysis of production data on tape width supplied by Patty's company correct in concluding that the process is predictable for tape width?

A: Yes, the process data as analyzed on an individuals and moving range chart shows that the process is predictable with an average width of 6.4988 and an average range of 0.013, which converts to a standard deviation of 0.118. See the chart, "Production Data for Tape Width."

Q: Is the customer's analysis of tape width correct in determining that the process producing the tape is unpredictable for tape width?

A: The customer's analysis also is correct in concluding that the process is not predictable for width of the tape. See the chart, "Tape Width in Shipment 81405 with Measurements Made by the Customer."

Q: Why is there a conflict in the

two analyses?

A: The conflict in these two analyses is a result of the measurement system used by each company. Patty's company uses a measuring device that records the tape width to the nearer 0.01 millimeter while the customer's data are recorded to the nearer 0.02 millimeter. This difference in resolution is typically a result of the choice of measuring device and the resolution setting. It is not uncommon to discover that the impact of measurement resolution on an analysis is poorly understood and rarely considered.

Q: What actions should Patty take to resolve this dilemma?

A: Patty and Graeme, the quality engineer, need to work with the customer to understand the impact that measurement resolution has on an analysis and then work with their customer to determine what measurement device and resolution should be used by both companies.

Dr. Sophronia Ward is a continual improvement specialist. Brain teasers are now incorporated in the new training programs, Six Sigma Training for Champions, Black Belts and Green Belts, offered by Dr. Ward and her associates at Pinnacle Partners Inc. For more information, call (865) 482-1362 or visit

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