News Blog readers know that the CLAHRC WM has a large interest in dissemination biases of various kinds. We recently featured an article on ‘p-hacking’, which can be unmasked by detecting a peak of findings with P values just below the fabled 0.05 threshold, as represented below.
Possible distribution of p-values around the null hypothesis.
Well, Ginsel, et al. analysed 2,000 abstracts selected at random from over 80,000 papers in medical journals. Sure enough, there was an overrepresentation between P values 0.05 and 0.049. The P value in this study was <0.001!
— Richard Lilford, CLAHRC WM Director
- Ginsel B, Aggawal A, Xuan W, Harris I. The distribution of probability values in medical abstracts: an observational study. BMC Res Notes. 2015; 8(1): 721.