WEIPLT
      SUBROUTINE WEIPLT(X,N,GAMMA)
  
PURPOSE--This subroutine generates a weibull probability plot
         (with tail length parameter value = GAMMA).  The proto-
         type weibull distribution used herein is defined for all
         positive X, and has the probability density function
         F(X) = GAMMA * (X**(GAMMA-1)) * EXP(-(X**GAMMA)).
         As used herein, a probability plot for a distribution
         is a plot of the ordered observations versus the order
         statistic medians for that distribution.  The weibull
         probability plot is useful in graphically testing the
         composite (that is, location and scale parameters need
         not be specified) hypothesis that the underlying
         distribution from which the data have been randomly
         drawn is the weibull distribution with tail length
         parameter value = GAMMA.  If the hypothesis is true,
         the probability plot should be near-linear.  A measure
         of such linearity is given by the calculated
         probability plot correlation coefficient.
INPUT  ARGUMENTS--X      = The single precision vector of
                           (unsorted or sorted) observations.
                --N      = The integer number of observations
                           in the vector X.
                --GAMMA  = The single precision value of the
                           tail length parameter.  GAMMA should
                           be positive
OUTPUT--A one-page weibull probability plot.
PRINTING--Yes.
RESTRICTIONS--The maximum allowable value of N for this
              subroutine is 7500.
            --GAMMA should be positive.
OTHER DATAPAC   SUBROUTINES NEEDED--SORT, UNIMED, PLOT.
FORTRAN LIBRARY SUBROUTINES NEEDED--SQRT, ALOG.
MODE OF INTERNAL OPERATIONS--Single precision.
LANGUAGE--ANSI FORTRAN.
REFERENCES--Filliben, 'Techniques for Tail Length Analysis',
            Proceedings of the Eighteenth Conference
            on the Design of Experiments Army Research
            Development and Testing (Aberdeen, Maryland,
            October, 1972), Pages 425-450.
          --Hahn and Shaprio, Statistical Methods in Engineering,
            1967, Pages 260-308.
          --Johnson and Kotz, Continuous Univariate
            Distributions--1, 1970, Pages 250-271.
WRITTEN BY--James J. Filliben
            Statistical Engineering Laboratory (205.03)
            National Bureau of Standards
            Gaithersburg, MD  20899
            Phone--  301-921-2315
ORIGINAL VERSION--December  1972.
UPDATED         --March     1975.
UPDATED         --September 1975.
UPDATED         --November  1975.
UPDATED         --February  1976.