Wha is a P value?

[VOLTOLINI]

Hi, I am impressed because in less than 24h 112 people sent me messages interested in to discuss the problem of teaching what is a P value.   After all these messages, I see that people are using two definitions:   The most frequent definition is: "P is the probability of getting a value of a test statistic equal to or greater than the one observed in your data, if it is a random pick from the distribution of the test statistic that would be created if a specified null hypothesis were true".   But also some people are using....."P-value is the probability of wrongly rejecting the null hypothesis".       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Prof. J. C. VOLTOLINI Grupo de Estudos em Ecologia de Mamiferos (ECOMAM) Universidade de Taubate, Departamento de Biologia Praca Marcelino Monteiro 63, Bom Conselho. Taubate, SP. CEP 12030-010. BRASIL. Tel: 0XX12 - 2254165 (Lab. Zool.) ou 2254277 (Depto. Biol.) E-Mail: [EMAIL PROTECTED] http://www.ecomam.hpg.ig.com.br ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   "Tutto di noi � un angelo con un'ala e possiamo volare soltanto se ci abbracciamo"