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« March 26, 2008 | Main | March 28, 2008 »

27 March 2008

How 0.05 comes into rule?

Recently I read an article written by Erin Leahey, talking about how the usage of statistical significance testing, the 0.05 cut-off value and the three-star system becomes legitimized and dominant in mainstream sociology. According to Erin, one star stands for p<=.05, two stars p<=.01 and three stars p<=.001. But I feel the cut-off values are something like .01, .05 and .10 respectively. Anyway, Erin attributed the first usage of .05 significance level to R. A. Fisher’s book, Design of Experiments in 1935. Erin noticed that other forms of significance testing besides the .05 test were already very popular in the 1930s, when close to 40 percent of articles published in ASR and AJS applied one or another form of significance testing procedure. Based on the articles she sampled from ASR and AJS, Erin showed that the popularity of the usage of statistical significance testing and the 0.05 cut-off value roughly took an “S” shape. The usage rose firstly from the 1930s to 1950, declined afterwards until 1970 and then revived since then. Currently, around 80 percent of articles published in ASR and AJS employ both practices. The three-star system emerged in the 1950s, but became popular only after 1970. Now there were slightly above 40 percent of articles published in the above top two sociological journals use this procedure.

So what account for the diffusion of such practices? Erin brought out several arguments to answer this question. For examples, she argued that institutional factors like investment in research and computer, graduate training and institution’s academic status, and journal editor’s individual preference, etc., could be some of the most important factors in the diffusion process of these practices. Interestingly, she found that graduating from Harvard had a significant negative “effect” on adopting these statistical practices. :-)

Of course, as it happens to almost all research, Erin’s study can not avoid some minor drawbacks either. For example, her sample is only drawn from the top two sociological journals and hence the generalization power of her findings could be limited. But overall, it is a fun reading. And if you are interested in more historical account of how the statistical practices were introduced to and became legitimized in social sciences in general, Camic and Xie (1994) is a very good start.

Leahey, Erin. 2005. Alphas and Asterisks: the Development of Statistical Significance Testing Standards in Sociology. Social Forces 84: 1-24.
Camic, Charles, and Yu Xie. 1994. “The Statistical Turn in American Social Science: Columbia University, 1890-1915.” American Sociological Review 59:773-805.

Posted by Weihua An at 11:57 AM