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Why Does ProbabilityScalePlot Display Censored Observations?

Posted 2 years ago
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I am attempting to reproduce a Weibull probability plot from Wayne Nelson's Applied Life Data Analysis text (pp. 147-9). I enter failure data for 16 field windings thus:

windingdata = {31.7, 39.2, 57.5, 65, 65.8, 70, 75, 75, 87.5, 88.3, 
   94.2, 101.7, 105.8, 109.2, 110, 130};

Seven of the observations are failures and nine are censored observations. In the list below each failure is denoted with a 0 and each right-censored observation is denoted with a 1:

censorlist = {0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1};

I use EventData to assemble these observations:

evdata = EventData[windingdata, censorlist]

I generate the probability plot thus:

ProbabilityScalePlot[evdata, "Weibull", 
 Method -> {"ReferenceLineMethod" -> "Fit"}]

The resulting plot includes points for the censored observations, in addition to points for the failures; this is not correct. While the censored observations are not plotted, they cannot simply be deleted --- they are needed in order to determine the plotting positions for the failure points. The reference info for ProbabilityScalePlot indicates that it accepts EventData.

Any help would be appreciated.

Michael Cushing

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