[R-sig-eco] Analyzing frequencies in R

[Phil Novack-Gottshall]

Dear Manuel,

You can use the Wilson method (with Yates' 
continuity correction) to calculate CIs for 
proportion data.  It's formally described and 
advocated in the following articles:

Newcombe R.G. (1998) Two-Sided Confidence 
Intervals for the Single Proportion: Comparison 
of Seven Methods. Statistics in Medicine 17, 857­872.
Newcombe R.G. (1998) Interval Estimation for the 
Difference Between Independent Proportions: 
Comparison of Eleven Methods. Statistics in Medicine 17, 873­890.

In R, it's implemented in prop.test (which also 
allows two-sample testing of equal proportions).

Cheers,
Phil



At 08:13 AM 6/8/2009, Manuel Spínola wrote:
>Dear list members,
>
>If I have 3 frequencies (3 mutually exclusive groups):
>
>white: 19
>black: 43
>red: 24
>
>How can I obtain confidence intervals for the 
>proportions, instead of a P value from a chisquare test in R?
>Or better, how can I assess "effect size" 
>instead of finishing the analysis on a P value when analyzing frequencies in R?
>Is it possible to obtain standardized Pearson residuals in this situation?
>Thank you very much in advance.
>Best,
>
>Manuel Spínola
>
>--
>Manuel Spínola, Ph.D.
>Instituto Internacional en Conservación y Manejo de Vida Silvestre
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   Phil 
Novack-Gottshall 
pnovackg at westga.edu

   Assistant Professor
   Department of Geosciences
   University of West Georgia
   Carrollton, GA 30118-3100
   Phone: 678-839-4061
   Fax: 678-839-4071
   http://www.westga.edu/~pnovackg
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~