.- help for ^wbull^ .-Fitting Weibull distribution by maximum likelihood --------------------------------------------------

^wbull^ varname [^if^ exp] [^in^ range] [weight] [, ^l^og ]

Description -----------

^wbull^ fits a Weibull distribution to a single variable by the method of maximum likelihood. Frequency weights may be used to fit variables given in frequency distribution form.

The distribution is here parameterised by a scale parameter b and a shape parameter c, so that the probability density function is

c - 1 c f(x) = (c / b) (x / b) exp(- (x / b) )

for x >= 0, b > 0 and c > 0.

The estimation is carried out by ^weibull^. Its _b[_cons] is ln b, and its [ln_p][_cons] is ln c.

Option ------

^log^ specifies that the results of ^weibull^ should be displayed.

Example -------

. ^wbull x^

Saved values ------------

S_1 number of values used S_2 ML estimate of b S_3 ML estimate of c

References ----------

Evans, M., Hastings, N. and Peacock, B. 1993. Statistical distributions. New York: John Wiley.

Johnson, N.L., Kotz, S. and Balakrishnan, N. 1994. Continuous univariate distributions: Volume 1. New York: John Wiley.

Author ------ Nicholas J. Cox, University of Durham, U.K. n.j.cox@@durham.ac.uk

Also see --------

Manual: [R] weibull On-line: help for @weibull@