Quality and Reliability Methods - SAS

220 Lifetime Distribution Chapter 13
Life Distribution Platform Options
Life Distribution Platform Options
The Life Distribution platform has the following options on the platform red triangle menu:
Fit All Distributions Shows the best fit for all distributions. Change the criteria for finding the best
distributions with the Comparison Criterion option.
Fit All Non-negative Fits all nonnegative distributions (Exponential, Lognormal, Loglogistic, Fréchet,
Weibull, and Generalized Gamma) and shows the best fit. If the data have negative values, then the
option produces no results. If the data have zeros, it fits all four zero-inflated (ZI) distributions,
including the ZI Lognormal, ZI Weibull, ZI Loglogistic, and the ZI Fréchet distributions. For details
about zero-inflated distributions, see “Zero-Inflated Distributions” on page 234.
Fit All DS Distributions Fits all defective subpopulation distributions. For details about defective
subpopulation distributions, see “Distributions for Defective Subpopulations” on page 234.
Show Points Shows or hides data points in the probability plot. The Life Distribution platform uses the
midpoint estimates of the step function to construct probability plots. When you deselect Show Points,
the midpoint estimates are replaced by Kaplan-Meier estimates.
Show Survival Curve Toggles between the failure probability and the survival curves on the Compare
Distributions probability plot.
Show Quantile Functions
Show Hazard Functions
Shows or hides the Quantile Profiler for the selected distribution(s).
Shows or hides the Hazard Profiler for the selected distribution(s).
Show Statistics
Tabbed Report
Shows or hides the Statistics report. See “Statistics Report” on page 216 for details.
Shows graphs and data on individual tabs rather than in the default outline style.
Show Confidence Area
Shows or hides the shaded confidence regions in the plots.
Interval Type The type of confidence interval shown on the Nonparametric fit probability plot (either
pointwise estimates or simultaneous estimates).
Change Confidence Level Lets you change the confidence level for the entire platform. All plots and
reports update accordingly.
Comparison Criterion
Lets you select the distribution comparison criterion.
Table 13.1 Comparison Criteria
Criterion Formula a Description
-2loglikelihood Not given Minus two times the natural log of
the likelihood function evaluated at
the best-fit parameter estimates
BIC
BIC = -2loglikelihood + kln( n)
Schwarz’s Bayesian Information
Criterion