There is a whole family of transformations for proportions usually refered as the Lambda-Tukey. Arcsine, logit and probit are members of this family. Logarithms can also work well but only under some conditions. You may check the chapter of Emerson in the book about Exploratory analysis of Variance by Hoagle, Mosteller and Tukey. ViSta has a graphical demonstration for these transformations.
Pedro At 15:50 17/10/2001 +0200, Tobias Richter wrote: >We have collected variables that represent proportions (i. e., the >proportion of sentences in a number of texts that belong to a certain >category). The distributions of these variables are highly skewed (the >proportions for most of the texts are zero or rather low). So my >question is: Is there a function that transforms the proportions into >symmetrically distributed variables? And is there a reliable statistics >text that discusses such transformations? > >Thank you very much, > >Tobias Richter > > > >-- >------------------------------------------------------------- >Tobias Richter, Psychological Dpt. (General Psychology) >University of Cologne (Germany) >Phone +49-(0)221-470 38 48 E-Mail [EMAIL PROTECTED] >http://www.allg-psych.uni-koeln.de/richter/trichter.htm > > >================================================================= >Instructions for joining and leaving this list and remarks about >the problem of INAPPROPRIATE MESSAGES are available at > http://jse.stat.ncsu.edu/ >================================================================= ========================================================== Dr. Pedro M. Valero-Mora. WWW: http://www.uv.es/~valerop Director M�todos de Investigaci�n Phone: +34 96 3393880 Fax: +34 96 3393881 Universitat de Val�ncia INTRAS-Instituto de Tr�fico y Seg. Vial. INTRAS-Institut of Traffic and Road Safety. C/ Hugo de Moncada 4. Entresuelo. Valencia, 46010, Espa�a (Spain). ========================================================== ================================================================= Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =================================================================
