Esta entrada abunda sobre una de la semana pasada sobre el llamado efecto Roseto. El Cournot al que alude el titulo es el Cournot famoso (1801-1877) al que, a pesar de ser más conocido por sus aportaciones a la economía, debemos una Exposition de la théorie des chances et des probabilités de 1843.
En su párrafo 114 critica explícitamente el tipo de conclusiones a las que llegan los descuidados exégetas del asunto Roseto y que Stigler comenta así:
Cournot’s rejection of the a posteriori meaningfulness of probability was not based on reservations about a priori assumptions on the unknown chances $latex x_1$ and $latex x_2$ such as might occur to a modern critic, but rather upon an acute awareness of the even more devastating effect that selecting a hypothesis after the data is at hand could have upon the conclusion. For emphasis, he supposed that one of the eighty-six departments of France exhibited a much larger ratio of male births than did all of France treated as a whole. For the corresponding a posteriori probability $latex \Pi$ to have an objective meaning, Cournot argued (pp. 197 - 198), it would be necessary that we know that the department in question was selected at random, as if its name were drawn from among eighty-six tickets in an urn and not merely singled out as the department with the largest male birth ratio among the eighty-six. But if the departments were selected at random or specified by the statistician prior to the analysis of the data, Cournot would have no difficulty accepting the a posteriori probability $latex \Pi$.