Trends in the Distribution of P Values in Epidemiology Journals: A Statistical, P-Curve, and Simulation Study

  • 0Department of Epidemiology, Brown University, Providence, RI.

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Summary

This summary is machine-generated.

Epidemiologists are shifting from P values to confidence intervals. Analysis shows P values have decreased, but this is likely due to increased statistical power, not reduced P hacking.

Area Of Science

  • Epidemiology
  • Biostatistics

Background

  • Concerns exist regarding null-hypothesis statistical-significance testing, P hacking, and reproducibility in epidemiology.
  • Epidemiologists have recommended reporting confidence intervals and reducing reliance on P values.

Purpose Of The Study

  • To investigate whether efforts to de-emphasize P values have altered their distribution in epidemiological research.
  • To analyze trends in P value distributions over time in major epidemiology journals.

Main Methods

  • Scraped P values (N=25,288) from 21,332 abstracts published between 2000-2024 in four major epidemiology journals using ChatGPT's 4o model.
  • Calculated P values from estimates and confidence intervals.
  • Evaluated trends over time and fitted to expected P value distributions, simulating scenarios with and without changes in statistical power.

Main Results

  • Average P values decreased from 2000 to 2024.
  • The proportion of P values falling just below the 0.05 significance threshold also decreased.
  • Model fits suggest an increase in statistical power over the study period.

Conclusions

  • The observed trends in P value distribution are consistent with increased statistical power, rather than a reduction in P hacking.
  • While the frequency of P values near the 0.05 threshold has modestly declined, this is attributed to enhanced statistical power.