Hello,
Was the variable used for the "pilot study" the main outcome measure of
interest? If so, then you must have known all the information necessary for
conducting a power study for a full blown clinical trial. That is, you must have
had some estimate of the variance and an estimate of the cli
Dear Professor Hoppe,
This is what I have presented to my students for many years to get the
concept discussed. Though you might like to see it.
A Great Deal? Or is it?
While you are wending your way home for an exciting day at school,
statistics being the farthest thing from
Dear Professor Hoppe,
This is what I have been presenting to my classes for many years. Thought
you might enjoy it.
A Great Deal? Or is it?
While you are wending your way home for an exciting day at school,
statistics being the farthest thing from your mind, you hear a sound.
2:16:35 -0600 (CST)
>From: David Cross/Psych Dept/TCU <[EMAIL PROTECTED]>
>Subject: Re: Power for Pilot Studies
>
>I do believe that to the extent there is a "conventional" alpha level,
>that level is .05. In the behavioral sciences, this convention is adhered
>to rathe
Seems to me that the notion of power in a pilot study is moot. Typically, a
pilot study is a test of the research methodology and instruments. As such,
your sample size is a pragmatic decision and should consist of enough
observations to test your design and research instruments. For instance, i
I do believe that to the extent there is a "conventional" alpha level,
that level is .05. In the behavioral sciences, this convention is adhered
to rather strictly, especially by journal editors and review panels!
On Wed, 15 Mar 2000, Andy Avins wrote:
> We proposed a pilot clinical trial that
Andy Avins wrote:
>
> Does anyone have any thoughts or references for sample size calculations
> for pilot studies?
In my neck of the woods, pilot studies are shake-down cruises
for figuring out to design the formal study. Sample size is
mostly a matter of covenience, logistics,...
If power ca
dennis roberts wrote:
>
> or, think about it this way ... what IF your p value had been
> .001 based on your pilot data ... why do any more? well, there
> are lots of reasons ...
depends on the field and the research question.
The association between Reye's syndrome and aspirin
was found in th
Andy,
I think Dennis has good points but I also have consulted in projects
that had to deal with local IRB's that get hung up on alpha (so I feel
your pain) You might want to look at:
Browne, R. H. (1995) On the use of a pilot sample for sample size
determination,
Statistics in Medicine 14, 19
well, this is interesting indeed ... for let's say that you did adopt a .1
level for a pilot AND, you just happened to reject the null IN the pilot
... is THAT sufficient justification for committing more time and resources
TO a large main study?? the implication from this pilot result is that
We proposed a pilot clinical trial that was shot down by a local review
committee. Lacking any other guidance, we arbitrarily chose an alpha of
0.25 for doing the power calculations (reasoning that we didn't want to set
too stringent a standard for rejecting the null and not proceeding with a
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