Chapter 8 – Performance Measurement and Information Management
1.
The rate of baggage mishandling reported by the Department of Transportation in the United
States was 3.75 per 1,000 passengers. If the average number of checked bags per passenger
is now 1.3, how many defects per million opportunities (DPMO) does this represent? How does
this compare with the rate given in the chapter – better or worse?
Answer
1.
dpmo = (Number of defects discovered) /opportunities for error x 1,000,000
Thus, a defect rate of 3.75 per 1,000 is equivalent to 3,750 dpmo if each passenger only had
one bag. However, customers may have different numbers of bags; thus the number of
opportunities for error must be based on the average number of bags per customer. If the
average number of bags per customer is 1.3, and the airline recorded 3.75 lost bags for 1000
passengers in a month, then
dpmo = 3.75/[1,000)(1.3)] x 1,000,000 = 2884.6
This number is considerably worse than the 234.375 hypothesized in the body of the chapter.
Chapter 11 – Six Sigma and Process Improvement
2.
During one month, 35 preflight inspections were performed on an airplane at Southstar
Airlines. Nine nonconformances were noted. Each inspection checks 30 items. What sigma
level does Southstar maintain if this incidence of nonconformance is typical of their entire fleet
of airplanes?
Answer
To calculate the dpmo, we use 9/35 to get the number of defects per unit (DPU’s). However,
30 opportunities per aircraft checked must be taken into consideration, as shown, in order to
calculate dpmo.
dpmo = (18/35) X 1,000,000/30 = 8571.4, which is less than 4 sigma with off centering of 1.5
sigma.
3.
Over the last year 1,054 injections were administered at the Fairhealth clinic. Quality is
measured by the proper amount of dosage as well as the correct drug. In two instances, the
incorrect amount was given, and in one case, the wrong drug was given. At what sigma level is
Fairhealth’s process?
Answer
We use 3/1054 to get the number of defects per unit (DPU’s). However, there are 2
opportunities per injection (wrong drug, wrong dosage) to make an error. They must be
considered, in order to calculate dpmo.
dpmo = (3/1054) X 1,000,000/2 = 1423.1, which is slightly less than 4.5 sigma with off centering of 1.5
sigma.