Thanks to Kit Baum, there is now a new version of -powercal- available for
download on SSC. In Stata, type
ssc desc powercal
to find out more.
-powercal- performs generalized power calculations, and is described as
below on my website. The new version still contains the same program, but I
have revised the on-line manual -powercal.pdf- and (to a lesser extent) the
help file. I have also certified the program with an improved certification
script, showing that -powercal- produces essentially the same results as
the official Stata -sampsi- command in a wide range of cases where their
functions overlap. (Type -findit cscript- in Stata to find out about
certification scripts.)
I have also placed a copy of the -powercal- manual -powercal.pdf- on my
website at http://www.kcl-phs.org.uk/rogernewson/
where it can be viewed using a browser or the Stata -net- command, so that
users can look at the Methods, Formulas and Examples before deciding
whether to install the package. The manual has the title "Generalized power
calculations", and presents a few generalized formulas covering a wide
range of power calculations for generalized linear model parameters and more.
Best wishes
Roger
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package powercal from http://www.kcl-phs.org.uk/rogernewson/stata7
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TITLE
powercal: Generalized power calculations saving results in variables
DESCRIPTION/AUTHOR(S)
powercal performs general power calculations, storing the result in
a new
variable, which can be plotted and/or listed. It can calculate any of 5
quantities, namely number of sampling units, power, alpha (significance
level), delta (difference in parameter value to be detected), or the
standard deviation (SD) of the influence function, defined as the
standard
error multiplied by the square root of the sample number. Each of
these 5
quantities is calculated using user-defined expressions for the other 4,
usually involving existing variables supplied by the user. powercal has
2 advantages over sampsi. First, it performs general power calculations,
not only power calculations for special cases such as differences
between
means and proportions. Second, it stores the results in variables, which
the user can list and/or plot on graphs.
Author: Roger Newson
Distribution-Date: 25nov2003
Stata-Version: 7
INSTALLATION FILES (click here to install)
powercal.ado
powercal.hlp
ANCILLARY FILES (click here to get)
powercal.pdf
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--
Roger Newson
Lecturer in Medical Statistics
Department of Public Health Sciences
King's College London
5th Floor, Capital House
42 Weston Street
London SE1 3QD
United Kingdom
Tel: 020 7848 6648 International +44 20 7848 6648
Fax: 020 7848 6620 International +44 20 7848 6620
or 020 7848 6605 International +44 20 7848 6605
Email: [email protected]
Website: http://www.kcl-phs.org.uk/rogernewson
Opinions expressed are those of the author, not the institution.
