Exercise 7

Section 4 Process Capability

Lesson S04-03

Text: Section 4 pages 16 & Section 9 page 13

Duration: 9 minutes

Introduction to Exercise 7

Batches of Blended Rubber to be used for O-Rings are tested with regard to hardness. Samples were taken and tested from 50 consecutive batches. The process has been shown to be stable and the individual values are normally distributed.

Summarized statistics from the data and specification limits follow:

Average (X-Bar) = 69.67
Std. Deviation (s) = 1.63
USL = 75.0
LSL = 65.0

Estimate the ppm (expected number of defective O-Rings per million produced)

Hints:

Draw a picture of the estimated distribution along with the specification limits relative to the distribution.
Use the formula for Z, once for the USL and once for the LSL.

Solution / Discussion of Exercise 7

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About Steven Wachs

Steven Wachs has 25 years of wide-ranging industry experience in both technical and management positions. Steve has worked as a statistician at Ford Motor Company where he has extensive experience in the development of statistical models, reliability analysis, designed experimentation, and statistical process control.