st: New version of -powercal- on SSC

["Roger B. Newson" <r.newson@imperial.ac.uk>]

Thanks as always to Kit Baum, a new version of the -powercal- package is 
now downloadable from SSC. In Stata, use the -ssc- command to do this, 
or -adoupdate- if you already have an old version of -powercal-.

The -powercal- package is described as below on my website, and performs 
power and sample size calculations in a dataset with 1 observation per 
scenario, calculating any of the 5 quantities power, alpha, detectable 
difference, sample size, and the standard deviation of the influence 
function from the other 4 quantities in the scenario, and storing the 
result in a new variable. This allows the user to produce power and 
sample size curves, rather than just point estimates. The new version is 
updated to Stata Version 10, and the examples in the online help, and in 
the .pdf manual, no longer use the old Stata Version 7 -graph- command. 
There is also a hypertext, in the online help, which directs the user to 
my 2004 Stata Journal article on -powercal- (Newson, 2004), which can 
now be downloaded free and gives a full set of methods and formulas.

Users of Stata Versions 7, 8 and 9 can still download the old Stata 
Version 7 version of -powercal- from my website by typing, in Stata,

net from http://www.imperial.ac.uk/nhli/r.newson/stata7

and selecting and installing -powercal-.

Best wishes

Roger

References

Newson R.  2004.  Generalized power calculations for generalized linear 
models and more.  The Stata Journal 4(4): 379-401.  Download from The 
Stata Journal website at
http://www.stata-journal.com/article.html?article=st0074

--
Roger B Newson BSc MSc DPhil
Lecturer in Medical Statistics
Respiratory Epidemiology and Public Health Group
National Heart and Lung Institute
Imperial College London
Royal Brompton Campus
Room 33, Emmanuel Kaye Building
1B Manresa Road
London SW3 6LR
UNITED KINGDOM
Tel: +44 (0)20 7352 8121 ext 3381
Fax: +44 (0)20 7351 8322
Email: r.newson@imperial.ac.uk
Web page: http://www.imperial.ac.uk/nhli/r.newson/
Departmental Web page:
http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgenetics/reph/

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

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package powercal from http://www.imperial.ac.uk/nhli/r.newson/stata10
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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. This package has an on-line
      manual powercal.pdf containing the Methods and Formulas and 
details on
      the Examples in the help file.

      Author: Roger Newson
      Distribution-Date: 26march2012
      Stata-Version: 10

INSTALLATION FILES                                  (click here to install)
      powercal.ado
      powercal.sthlp

ANCILLARY FILES                                     (click here to get)
      powercal.pdf
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