Date:         Wed, 7 Dec 2011 14:00:48 -0400
Reply-To:     Gerónimo Maldonado
              <geronimo.maldonado@gmail.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Gerónimo Maldonado
              <geronimo.maldonado@gmail.com>
Subject:      Sample size and loss of subjects in an experiment
Content-Type: multipart/alternative;

Hi Experts:

From theory I know that any sample size calculation is based on the total
number of subjects who are needed in a particular study. In practice,
eligible subjects will not always be willing to take part on the study and
it will be necessary to approach more subjects than are needed in the first
instance. My question is: How can I account for those subjects who refuse
to participate? Is there any method or equation to account for something
that is called "loss factor"?.  In example... A sample size calculation
told me that I need 400 subjects (200 men / 200 female) to reject the null
hypothesis of certain experiment... but I want to adjust that sample size
in case I loss some of the subjects of any stratum. How can I do that?... A
thought...


Thanks in advance!

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