From an article in Science:
The average number of P values per paper has been steadily rising, they found. A typical paper now reports 10 P values, double the number from the 1980s. This suggests that researchers are conducting more experiments than before or exploring more variables. In other words, ecological research is getting more complex. A scientist trying to predict algal blooms probably has an equation that considers not just phosphorus levels, but also temperature, water clarity, and many other factors.
But the proliferation of P values (which is happening in many fields) concerns statisticians, because the value by itself doesn’t say anything about the size of the effect or its biological significance. “You can get quite trivial findings” that have robust P values, Low-Décarie says. Nearly half of all papers in the database that reported a P value, for example, did not appear to include other statistics that would clarify for readers whether the result had a major ecological impact. In addition, the more P values that are calculated, the higher the odds that any given result will appear to be significant even if it’s just the result of chance.
The researchers were more surprised and dismayed to discover that R2—a more informative statistical indicator—has been on the decline. In 1980, the average R2 reported in papers was about 0.7. By 2010, it had fallen to just under 0.5, they report online this month in Frontiers in Ecology and the Environment. “That was really surprising to me,” says Brian McGill, an ecologist at the University of Maine, Orono, who was not involved in the research. The average R2 should be increasing, he says, because more variables are being included in ecological models, which ought to make them more accurate. More.
We’ll keep an eye on this one. Follow UD News at Twitter!