Forest Products Laboratory





Computer code for predictor sort power calculations

We have developed computer code that performs large sample analytic predictor sort power calculations and checks some of these estimates for small samples using simulations. The large sample results and the small sample simulation programs are based upon research reported in Verrill (1993), "Predictor Sort Sampling, Tight T's, and the Analysis of Covariance," The Journal of the American Statistical Association, 88, No. 421, 119-124 (pdf) and Verrill and Kretschmann (2015), "A Reminder about Potentially Serious Problems with a Type of Blocked ANOVA Analysis," USDA Forest Products Laboratory draft research paper (pdf).

The programs can be run over the Web at http://www1.fpl.fs.fed.us/sampsize.html. The material below provides links to FORTRAN versions of this computer code.

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FORTRAN code

The FORTRAN sssimp source code (power calculations in the simple 1 factor, 2 levels case) comes in two files:

  1. sssimp.f --- A main routine written by Steve Verrill.
  2. quadint.f --- A quadratic interpolation subroutine written by Steve Verrill.

The sssimp program also depends upon DCDFLIB. DCDFLIB is a public domain library of "routines for cumulative distribution functions, their inverses, and their parameters." It was produced by Barry Brown, James Lovato, and Kathy Russell of the Department of Biomathematics, M.D. Anderson Cancer Center, The University of Texas. DCDFLIB can be found at https://biostatistics.mdanderson.org/SoftwareDownload/SingleSoftware.aspx?Software_id=21 .

The FORTRAN sscomp.2 source code for power calculations involving a comparison of 2 pre-specified levels of a factor in the complex case (possibly more than two factors, possibly more than two levels per factor) comes in one file:

  1. sscomp.2.f --- A main routine written by Steve Verrill.

The sscomp.2 program also depends upon the DCDFLIB library described above.

The FORTRAN simcomp.2 source code for simulation estimates of power for a comparison of 2 pre-specified levels of a factor in the complex case (possibly more than two factors, possibly more than two levels per factor) comes in four files:

  1. simcomp.2.f --- A main routine written by Steve Verrill.
  2. rnor.f --- rnor is a routine that "generates quasi normal random numbers, with mean zero and unit standard deviation." It was written by David Kahaner and George Marsaglia.
  3. rsort.f --- A routine that sorts real numbers. Written by Steve Verrill.
  4. slat.f --- Routines from the public domain SLATEC package of numerical analysis routines.

The simcomp.2 program also depends upon the DCDFLIB library described above, and on the public domain LAPACK package of linear algebra numerical analysis routines. This library can be found at http://www.netlib.org/lapack/.

The FORTRAN sscomp.mult source code for power calculations involving a comparison of all levels of a factor in the complex case (possibly more than two factors, possibly more than two levels per factor) comes in one file:

  1. sscomp.mult.f --- A main routine written by Steve Verrill.

The sscomp.mult program also depends upon the DCDFLIB library described above.

The FORTRAN simcomp.mult source code for simulation estimates of power for a comparison of all levels of a factor in the complex case (possibly more than two factors, possibly more than two levels per factor) comes in four files:

  1. simcomp.mult.f --- A main routine written by Steve Verrill.
  2. rnor.f --- rnor is a routine that "generates quasi normal random numbers, with mean zero and unit standard deviation." It was written by David Kahaner and George Marsaglia.
  3. rsort.f --- A routine that sorts real numbers. Written by Steve Verrill.
  4. slat.f --- Routines from the public domain SLATEC package of numerical analysis routines.

The simcomp.mult program also depends upon the DCDFLIB library described above, and on the public domain LAPACK package of linear algebra numerical analysis routines. This library can be found at http://www.netlib.org/lapack/.

Support

If you have questions about this software, or suggestions for improvement, please contact Steve Verrill at sverrill@fs.fed.us or 608-231-9375.

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Last modified on 5/16/15.

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