A Fortran computer program has been written for performing statistical analysis of fatigue-test data that are assumed to be adequately represented by a two-parameter Weibull distribution. This program calculates the following:

  • Maximum-likelihood estimates of the Weibull distribution;
  • Data for contour plots of relative likelihood for two parameters;
  • Data for contour plots of joint confidence regions;
  • Data for the profile likelihood of the Weibull-distribution parameters;
  • Data for the profile likelihood of any percentile of the distribution; and
  • Likelihood-based confidence intervals for parameters and/or percentiles of the distribution.

The program can account for tests that are suspended without failure (the statistical term for such suspension of tests is "censoring"). The analytical approach followed in this program for the software is valid for type-I censoring, which is the removal of unfailed units at pre-specified times. Confidence regions and intervals are calculated by use of the likelihood ratio method.

This program was written by Timothy L. Krantz of the Vehicle Technology Center of the U.S. Army Research Laboratory for Glenn Research Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Software category. Inquiries concerning rights for the commercial use of this invention should be addressed to

NASA Glenn Research Center, Commercial Technology Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135.

Refer to LEW-17401-1.

NASA Tech Briefs Magazine

This article first appeared in the September, 2005 issue of NASA Tech Briefs Magazine.

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