La Moqueta Verde


Nota metodológica: ¡Atención con las interacciones!

Cuando sólo el 10% de los artículos publicados en revistas académicas de Ciencia Política especifican correctamente las interacciones en sus modelos es que algo muy preocupante ocurre en nuestra disciplina. Lean lo que he encontrado en uno de nuestros blogs favoritos, New Economist (citando a orgtheory):

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As noted by Branbor, Clark and Golder (2006) in a recent article in Political Analysis, a survey of 156 articles published in the major Political Science journals shows that only 10% of researchers specified their interaction models correctly. A large chunk of them outright omitted main effects, which can lead to incorrect significance tests of the interaction term. In some of these articles the entire contribution was riding on the interaction term. So things are not so simple. Consider the horror:

In an award-winning article in the American Political Science Review, Boix (1999) examines the factors that determine electoral system choice in advanced democracies. He makes two main conclusions. First, ethnic or religious fragmentation encourages the adoption of proportional representation in small and medium-sized countries (621). He draws this conclusion based on a model that includes an interaction term between ethnoreligious fragmentation and country size. However, he does not include either of the constitutive terms. When these terms are included, there is no longer any evidence that ethno-religious fragmentation ever affects the adoption of proportional representation (italics added).
You should read the article to see other horror stories. The lesson: if your dissertation/paper is riding on an interaction effect, don’t be a fool. Estimate a fully specified model.
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...Y que me disculpen los lectores que no estén familiarizados con la econometría.

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2 Respuestas a “Nota metodológica: ¡Atención con las interacciones!”

  1. # Blogger el 10

    A los tantos trabajos que no incluyen los efectos principales en sus modelos econométricos, hay que sumarle todos aquellos que interpretan mal el coeficiente de interacción, pues suelen olvidar restar dicho efecto principal.
    Del primer caso, yo me se de uno que frecuenta mucho la moqueta verde… de hecho, es el jefe! (véase su último WP). Aunque lo peor es que luego algunos van y lo copian… mmm… así mal vamos.
    Del segundo también conozco a otro moquetero… yo mismo!

    Abrazos.  

  2. # Blogger Alex Guerrero

    De hecho, tampoco es tan grave, dado que el 50% de los artículos publicados en journals de Ciencia (la hardcore, no la nuestra) están mal.

    ;-)

    Scientist Says Most Scientific Papers are Wrong

    "According to epidemiologist John Ioannidis, the majority of published scientific papers are wrong. If Ioannidis's own paper is right, a randomly chosen scientific paper has less than a 50% chance of being true. He also says that many papers may only be accurate measures of the prevailing bias among scientists. However, a senior editor of a scientific journal says that scientists are already aware of this: 'When I read the literature, I'm not reading it to find proof like a textbook. I'm reading to get ideas. So even if something is wrong with the paper, if they have the kernel of a novel idea, that's something to think about.'"  

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