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st: New version of -powercal- on SSC


From   Roger Newson <roger.newson@kcl.ac.uk>
To   statalist@hsphsun2.harvard.edu
Subject   st: New version of -powercal- on SSC
Date   Wed, 26 Nov 2003 16:29:03 +0000

Hello All

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

---------------------------------------------------------------------------------
package powercal from http://www.kcl-phs.org.uk/rogernewson/stata7
---------------------------------------------------------------------------------

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
---------------------------------------------------------------------------------

--
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: roger.newson@kcl.ac.uk
Website: http://www.kcl-phs.org.uk/rogernewson

Opinions expressed are those of the author, not the institution.

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