Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

Re: st: Power calculation and sample sizes


From   Jeph Herrin <[email protected]>
To   [email protected]
Subject   Re: st: Power calculation and sample sizes
Date   Fri, 17 Aug 2007 09:38:05 -0400

You might find this helpful

  http://www.stata.com/support/faqs/stat/power.html

hth,
Jeph


Vieira, Cecilia wrote:
Dear All,

I would like to determine the sample size for a RCT. Control and intervention
groups will have the same size.
The intention of the intervention is to increase a certain preventive measure
among patients. We will measure prevalence of the preventive measure at baseline for both groups
and expect to find that 20% of all the patients (control and intervention) adopt
the measure before the experiment.
We would like to be able to detect a change from 20% to 40% in the intervention
group, while we expect that the control group will change their adoption rates
from 20% to 25%.

My first plan was to simulate some samples, starting with some hypothetical
sample size, then run a logistic model multiple times, and calculate power as a
proportion of times when the expected coeficients were significant. Then repeat
the simulations for different sample sizes until I could had an idea of sample
size versus power.

I would like to hear from you if there is a simple command in stata that gives
me the result more easily.

Thank you.

Cecilia


The information transmitted in this electronic communication is intended only for the person or entity to whom it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of or taking of any action in reliance upon this information by persons or entities other than the intended recipient is prohibited. If you received this information in error, please contact the Compliance HelpLine at 800-856-1983 and properly dispose of this information.


*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/


*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2024 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index