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| '''Published 3P Weibull Distribution Probability Plot Example'''
| | #REDIRECT [[Weibull Distribution Examples]] |
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| From Dimitri Kececioglu, Reliability & Life Testing Handbook, Page 406. [[Appendix: Weibull References|[20]]].
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| Estimate the parameters for three-parameter Weibull, for a sample of ten units all tested to failure. The times-to-failure were recorded at 200; 370; 500; 620; 730; 840; 950; 1,050; 1,160; and 1,400 hours.
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| '''Published Results:'''
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| Published results (using probability plotting):
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| [[Image:example19formula.png|center]]
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| '''Computed Results in Weibull++'''
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| Weibull++ computed parameters for rank regression on X are:
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| [[Image:compexample19formula.png|center]]
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| The small difference between the published results and the ones obtained from Weibull++ are due to the difference in the estimation method. In the publication the parameters were estimated using probability plotting (i.e. the fitted line was "eye-balled"). In Weibull++, the parameters were estimated using non-linear regression (a more accurate, mathematically fitted line). Note that γ in this example is negative. This means that the unadjusted for γ line is concave up, as shown next.
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| [[Image:Weibull Distribution Example 19 Plot.png|center|250px]] | |