Wuensch, Karl L wrote:
> Better to find power for the smallest effect that you would consider not to be
>trivial in
> magnitude. If that power is high, then you can make a strong statement
> regardless of whether your effect is "statistically significant" or not.
Well, yes, but the statement that you would make would be "I had sufficient
power to find an effect of the hypothesized magnitude. I failed to find that effect,
which (strongly?) suggests that in fact the effect does not exist".
(I'm sure you meant to imply that - I just want to be sure that this doesn't come
across as "if your power is high, that means that you found the effect that you were
looking for").
Paul Smith
Alverno College
Milwaukee
-----Original Message-----
From: Noel Kinder [mailto:nkinder@;psyc.umd.edu]
Sent: Tuesday, November 12, 2002 8:47 AM
To: Teaching in the Psychological Sciences
Subject: Re: SPSS & Power
Dear Rob,
In SPSS 11.0 it is possible to calculate the estimated power for ANOVAs.
I have not tried this for a one-way ANOVA however.
>From the Help guide for "GLM Univariate Options..."
"Display...Select Observed power to obtain the power of the test when
the alternative hypothesis is set based on the observed value. Select
Parameter estimates to produce the parameter estimates, standard errors,
t tests, confidence intervals, and the observed power for each test..."
My favorite power resource is G*Power. G*Power is an excellent power
estimation tool. While there are limitations to the tests it applies to,
it does cover ANOVAs. In addition, I recommend G*Power to people BEFORE
they start research for getting your needed sample size. It is easy to
get your sample size when you enter your desired power and effect size.
To get G*Power (free), you go to:
http://www.psycho.uni-duesseldorf.de/aap/projects/gpower/index.html
How to Use G*Power
http://www.psycho.uni-duesseldorf.de/aap/projects/gpower/how_to_use_gpower.h
tml
Enjoy
Noel Kinder, MA
was University of Maryland PhD Student
now Child Welfare League of America Research Specialist
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