Meta-assessment of bias in science

Significance Science is said to be suffering a reproducibility crisis caused by many biases. How common are these problems, across the wide diversity of research fields? We probed for multiple bias-related patterns in a large random sample of meta-analyses taken from all disciplines. The magnitude of these biases varied widely across fields and was on average relatively small. However, we consistently observed that small, early, highly cited studies published in peer-reviewed journals were likely to overestimate effects. We found little evidence that these biases were related to scientific productivity, and we found no difference between biases in male and female researchers. However, a scientist’s early-career status, isolation, and lack of scientific integrity might be significant risk factors for producing unreliable results.