Chapter 9 Instructor Reserve Problems
The following problems may be used for in-class illustrations, workshops, or additional
homework assignments to supplement those in the text.
1. Ultraprecision Corp. has historically had processes which operate above the five sigma
level. They have a new process on which they are about to start production. If the
specification for a critical part produced by the process is 3.5 cm ± 0.10 and the standard
deviation for the process is 0.019, at what sigma level is this process operating?
2. Nodroptcalz Cellphone Co. advertises that 99% of their customer’s calls are completed
without interruption. How many dpmo does this claim represent? At what sigma level is
this process operating, assuming a 1.5 sigma offset?
3. Jack Frost has used his belt-driven, hand-guided snowblower to clear his driveway for
several winters. Due to a knee replacement, he can’t do the work this winter. He wants to
make a flowchart to assist his 15-year old son in knowing what steps to follow when he
takes over the job. Assume that the blower is stored in the garage. Some of the steps
would include getting it out of the garage, blowing the snow off the driveway, and
putting it back in the garage. Are there other steps that should be included, in order to
have a more complete flowchart? Construct the flowchart, using Excel, or other
appropriate software having drawing tools.
4. The times required to assemble a common circuit board at Circuitus Corp. were
measured. The production manager thought that the assembly times increased as the day
progressed, due to worker fatigue. A typical worker was chosen and three assembly times
were taken and averaged for each hour of the workday over a period of 5 workdays.
These averages are provided in the worksheet Prob. 9-4. Construct a histogram and a
scatter diagram of the data. What suggestions would you give the production manager?
5. A kiln at Suither Pottery was thought to be unstable, due to the number of defective items
that were being experienced. To test this theory, the temperature was measured every
hour over a 36 hour cycle. The temperature range was required to be 1180 ± 20 deg. C.
The results can be found in the worksheet Prob. 9-5. Construct a scatter diagram for these
data. What conclusions can you reach?
6. Weights of containers filled with a powdered dietary supplement made by WeightBgone
were measured by taking samples for 30 days consisting of 4 containers, each. The data
found in the worksheet Prob. 9-6 were gathered by a quality analyst. The containers were
designed to be filled with 400 ± 20 grams. Construct a histogram of the data. What can
you observe about the shape of the distribution? What would you recommend to the
production manager based on your analysis? Construct a control chart for the data. What
additional information does it provide?