How unbiased statistical methods lead to biased scientific discoveries: A case study of the Efron-Petrosian statistic applied to the luminosity-redshift evolution of Gamma-Ray Bursts

TL;DR

This paper demonstrates that using the Efron-Petrosian statistic without considering its assumptions can lead to biased conclusions about Gamma-Ray Burst evolution, emphasizing the importance of accounting for detection thresholds.

Contribution

The study reveals how improper application of the Efron-Petrosian method biases results and highlights the significance of detection threshold effects in LGRB evolution studies.

Findings

Detection thresholds are often underestimated in LGRB studies.

Incomplete samples can produce spurious luminosity-redshift correlations.

Monte Carlo simulations support the impact of detection biases.

Abstract

Statistical methods are frequently built upon assumptions that limit their applicability to certain problems and conditions. Failure to recognize these limitations can lead to conclusions that may be inaccurate or biased. An example of such methods is the non-parametric Efron-Petrosian test statistic used in the studies of truncated data. We argue and show how the inappropriate use of this statistical method can lead to biased conclusions when the assumptions under which the method is valid do not hold. We do so by reinvestigating the evidence recently provided by multiple independent reports on the evolution of the luminosity/energetics distribution of cosmological Long-duration Gamma-Ray Bursts (LGRBs) with redshift. We show that the effects of detection threshold has been likely significantly underestimated in the majority of previous studies. This underestimation of detection threshold leads to severely-incomplete LGRB samples that exhibit strong apparent luminosity-redshift or energetics-redshift correlations. We further confirm our findings by performing extensive Monte Carlo simulations of the cosmic rates and the luminosity/energy distributions of LGRBs and their detection process.