Page 454 - Six Sigma Demystified

434 Six SigMa DemystifieD

8. d.
9. d. Special causes of variation, by definition, occur when a subgroup exceeds the
statistical limits established in a properly designed statistical process control
chart.
10. a. Process histograms are inappropriate tools for analyzing variation until the
process is shown to be in statistical control. Special causes of variation must be
identified and their causes considered relative to the expected project benefits.
Confidence intervals are appropriate tools for populations rather than processes
and are the incorrect tool for detection of special causes of variation.
Chapter 6: analyze Stage
1. d. Inspection is not value-added because it does not change form, fit, or function.
Choice b is incorrect because it confuses a value-added task with the business
value-added scenario where the inspection is needed owing to poor process
quality. Choice c is incorrect in implying that sampling inspection will ensure
that customer receives only acceptable product.
2. b.
3. d.
4. d.
5. d.
6. a. Increasing batch size increases the time required to produce a given unit of
production because the given unit must wait for the remainder of the batch to
be completed. Setup simplification, rather than adding complexity, will reduce
setup time.
7. d.
8. c.
9. d.
10. c. Failing to recognize interaction may prevent detection of the interacting
factors as being significant.

Chapter 7: improve Stage

1. c. Efforts to reduce cycle time always should be evaluated for their impact on
quality
2. d.
3. c. Useful simulations can be run using rather simple software on a laptop.
4. c. In at least some cases, the overall objective in using simulations is to prevent
future instances of process errors. While the data generated by a simulation may
more precisely model a particular distribution, the actual process data provide
the benchmark to which the accuracy of the simulated data can be evaluated. In
this regard, the process data, by definition, provide the exact model for the
process.
5. c.
6. c. Evolutionary operations (EVOP) allows the process to continue to generate
product.
7. a.
8. d.