Thanks to Kit Baum, there is now a new version of the -powercal- package 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 has improved code, which sets
undefined results to missing, and has a manual -powercal.pdf-, which
contains the Methods and Formulas and some Examples. I would like to thank
Stanislav Kolenikov for posting his FAQ on the lognormal distribution on
his website at http://www.komkon.org/~tacik/
which I have found very useful for doing lognormal power calculations, such
as Example 1 in -powercal.pdf-.
Best wishes
Roger
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package powercal from http://www.kcl-phs.org.uk/rogernewson/stata7
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TITLE
powercal: General power and sample size calculations stored 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 the special cases of differences between means and proportions.
Second, it stores the results in variables, which the user can list
and/or
plot.
Author: Roger Newson
Distribution-Date: 18nov2003
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.
