O papel da plausibilidade na avaliação da pesquisa científica

Abstract

The paper discusses the impact of plausibility (the a priori probability) on the results of scientifi c research, according to the approach proposed by Ioannidis, concerning the percentage of null hypotheses erroneously classifi ed as "positive" (statistically signifi cant). The question "what fraction of positive results are true-positives?", which is equivalent to the positive predictive value, is dependent on the combination of true and false hypotheses within a given area. For example, consider an area in which 90% of hypotheses are false and α = 0.05 and power = 0.8: for every 1,000 hypotheses, 45 (900 x 0.05) are false-positives and 80 (100 x 0.8) are true-positives. Therefore, the probability of a positive result being a false-positive is 45/125. In addition, the reporting of negative results as if they were positive would contribute towards an increase in this fraction. Although this analysis is diffi cult to quantify, and these results are likely be overestimated, it has two implications: i) plausibility should be considered in the analysis of the ethical adequacy of a research proposal, and ii) mechanisms aimed at registering studies and protocols should be encouraged.