Six Sigma SPC OEM Products
Six Sigma and SPC (Statistical Process Control) Software
Applications
Six Sigma SPC - 2070 W. Washington St. #5
Springfield IL 62702 Ph: 217.698.0063
6 Sigma Statistical Process Control (SPC) Software for Windows
95/98/NT/2000/XP/ME

A statistical approach, using graphical
plots of the time-to-failure. A family of distributions that evaluates a
design and is used to deduce the percentage of failures of a design?s
population for a given time all the way through a design’s life
expectancies.

The distributions typically use the
formula of?

You can make predictions using a Weibull
Probability Distribution, but it can be cumbersome, and the predictions
are usually plotted on Weibull probability
paper, but to make a valid Weibull plot, at least seven points are
needed. Any fewer can cast doubt on the ability of a plot to see any
underlying pattern of variation.

A plot could look like the following.

The example below is from the Dale H.
Besterfield, Ph.D. book, Quality
Control Sixth Edition, that includes a CD of Excel macros.

For another example, see the National
Institute of Standards and Technology’s pages titled Weibull
Distribution and Weibull
Plot