Capicúa

Capicúa es una de las trescientas cincuenta y pico palabras españolas que tienen su origen en el idioma catalán. Significa _cabeza _y cola. Y viene muy bien para etiquetar las dos entradas que, con esta, he realizado sobre las elecciones en Cataluña.

La que hice en su día, la cola, criticaba los métodos y ponía en cuestión los resultados de una encuesta electoral realizada por El Periódico (para más información, véase este enlace). Tal vez no sea casualidad que el software usado por los analistas en este caso sea SPSS.

La cabeza este otro análisis de la misma materia elaborado por Xavier Fernández-i-Marín (y usando, en este caso, R). Está basado en el artículo Pooling the polls over an election campaign de Simon Jackman y en cuyo resumen se lee:

Poll results vary over the course of a campaign election and across polling organisations, making it difficult to track genuine changes in voter support. I present a statistical model that tracks changes in voter support over time by pooling the polls, and corrects for variation across polling organisations due to biases known as ‘house effects’. The result is a less biased and more precise estimate of vote intentions than is possible from any one poll alone. I use five series of polls fielded over the 2004 Australian federal election campaign (ACNielsen, the ANU/ninemsn online poll, Galaxy, Newspoll, and Roy Morgan) to generate daily estimates of the Coalition’s share of two-party preferred (2PP) and first preference vote intentions. Over the course of the campaign there is about a 4 percentage point swing to the Coalition in first preference vote share (and a smaller swing in 2PP terms), that begins prior to the formal announcement of the election, but is complete shortly after the leader debates. The ANU/ninemsn online poll and Morgan are found to have large and statistically significant biases, while, generally, the three phone polls have small and/or statistically insignificant biases, with ACNielsen and (in particular) Galaxy performing quite well in 2004.

Ojalá tuviesen estos estudios mayor repercusión mediática…