[R] power?

Simon Blomberg s.blomberg1 at uq.edu.au
Wed Oct 7 08:35:58 CEST 2009


The short answer is Yes. If you reject the null hypothesis based on that
p-value, then by definition you had enough power to do that. This is
because there is a precise inverse relationship between the p-value and
the "observed" power, once you fix the effect size and the sample size.
In other words, your post-hoc power analysis would be a simple
re-statement of the p-value. There is no extra information that can be
gained from such an analysis. See:

The American Statistician, February 2001, Vol. 55, No. 1, pp 19-24

Don't bother with your power analysis, unless you are planning a new
experiment.

Simon.

On Tue, 2009-10-06 at 13:49 -0700, SNN wrote:
> Hi,
> 
> I have used multiple linear regression on a data set and one if the
> regressor was significant with a p-value =0.01
> 
> I need to calculate the power for a multiple linear regression. i.e. do I
> have enough power to believe the above p-value?
> 
> 
> 
>  


-- 
Simon Blomberg, BSc (Hons), PhD, MAppStat. 
Lecturer and Consultant Statistician 
School of Biological Sciences
The University of Queensland 
St. Lucia Queensland 4072 
Australia
Room 320 Goddard Building (8)
T: +61 7 3365 2506
http://www.uq.edu.au/~uqsblomb
email: S.Blomberg1_at_uq.edu.au

Policies:
1.  I will NOT analyse your data for you.
2.  Your deadline is your problem.

Statistics is the grammar of science - Karl Pearson



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