文档介绍：Distribution –Weibull
Purpose
To make predictions regarding a population applicable in describing a wide variety of
patterns of variation, including departures from the normal and exponential.
This distribution covers many shapes of distributions thus reducing the problem of
deciding which of mon distributions (. normal or exponential) best fits a set of
data
Anatomy
The Weibull Distribution
A
C
α= Scale parameter
2
β= Shape parameter
n
o α= 1 α= 1
i
t
c β= β= 4
n
u
f
l
l
u
b
i
e α= 1
1
W
β= 1
e
h
t
f
o α= 1
e β
u = 2
l
a
V
0
1
B X
Six Sigma - Tools & Concepts DistWeib_001
Reference: Juran’s Quality Control Handbook - Ch. 23, P. 34-37
The pdf is
axa-1 * e-(x/b)2
f(x) = --------------------- x > 0
ba
Terminology
A. Vertical axis - Scale to measure the value of the Weibull function.
B. Horizontal axis - Scale of measure of the independent variable (X).
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C. Curves representing the Weibull Distribution for different values of its parameters β, α
and g.
β(Beta) Shape parameter - Reflects the pattern of the curve. When β= the
Weibull function reduces to the exponential function and when β is about
(and α