Selective Hypothesis Reporting in Psychology: Comparing Preregistrations and Corresponding Publications

In this study, we assessed the extent of selective hypothesis reporting in psychological research by comparing the hypotheses found in a set of 459 preregistrations with the hypotheses found in the corresponding articles. We found that more than half of the preregistered studies we assessed contained omitted hypotheses ( N = 224; 52%) or added hypotheses ( N = 227; 57%), and about one-fifth of studies contained hypotheses with a direction change ( N = 79; 18%). We found only a small number of studies with hypotheses that were demoted from primary to secondary importance ( N = 2; 1%) and no studies with hypotheses that were promoted from secondary to primary importance. In all, 60% of studies included at least one hypothesis in one or more of these categories, indicating a substantial bias in presenting and selecting hypotheses by researchers and/or reviewers/editors. Contrary to our expectations, we did not find sufficient evidence that added hypotheses and changed hypotheses were more likely to be statistically significant than nonselectively reported hypotheses. For the other types of selective hypothesis reporting, we likely did not have sufficient statistical power to test for a relationship with statistical significance. Finally, we found that replication studies were less likely to include selectively reported hypotheses than original studies. In all, selective hypothesis reporting is problematically common in psychological research. We urge researchers, reviewers, and editors to ensure that hypotheses outlined in preregistrations are clearly formulated and accurately presented in the corresponding articles.