Showing posts with label cognitive bias. Show all posts
Showing posts with label cognitive bias. Show all posts

Wednesday, April 14, 2021

Bias in Assessing Cognitive Bias in Forensic Pathology: The Dror Nevada Death Certificate "Study"

Following the longest hiatus in the history of the Medical Evidence Blog, I return to issues of forensic medicine, by happenstance alone. In today's issue of the NYT is this article about bias in forensic medicine, spurred by interest in the trial of the murder of George Floyd. Among other things, the article discusses a recently published paper in the Journal of Forensic Sciences for which there were calls for retraction by some forensic pathologists. According to the NYT article, the paper showed that forensic pathologists have racial bias, a claim predicated upon an analysis of death certificates in Nevada, and a survey study of forensic pathologists, using a methodology similar to that I have used in studying physician decisions and bias (viz, randomizing recipients to receiving one of two forms of a case vignette that differ in the independent variable of interest). The remainder of this post will focus on that study, which is sorely in need of some post-publication peer review.

The study was led by Itiel Dror, PhD, a Harvard trained psychologist now at University College London who studies bias, with a frequent focus on forensic medicine, if my cursory search is any guide. The other authors are a forensic pathologist (FP) at University of Alabama Birmingham (UAB), a FP and coroner in San Luis Obispo, California, a lawyer with the Clark County public defender's office in Las Vegas, Nevada, a PhD psychologist from Towson University in Towson, Maryland, an FP proprietor of a Forensics company who is a part time medical examiner for West Virginia, and an FP who is proprietor of a forensics and legal consulting company in San Francisco, California. The purpose of identifying the authors was to try to understand why the analysis of death certificates was restricted to the state of Nevada. Other than one author's residence there, I cannot understand why Nevada was chosen, and the selection is not justified in the paltry methods section of the paper.

Tuesday, April 1, 2014

Absolute Confusion: How Researchers Mislead the Public with Relative Risk

This article in Sunday's New York Times about gauging the risk of autism highlights an important confusion in the appraisal of evidence from clinical trials and epidemiological studies that appears to be shared by laypersons, researchers, and practitioners alike:  we focus on relative risks when we should be concerned with absolute risks.

The rational decision maker, when evaluating a risk or a benefit, is concerned with the absolute magnitude of that risk or benefit.  A proportional change from an arbitrary baseline (a relative risk) is irrelevant.  Here's an example that should bring this into keen focus.

If you are shopping and you find a 50% off sale, that's a great sale.  Unless you're shopping for socks.  At $0.99 a pair, you save $0.50 with that massive discount.  Alternatively, if you come across a 3% sale, but it's at the Audi dealership, that paltry discount can save you $900 on a $30,000 Audi A4.   Which discount should you spend the day pursuing?  The discount rate mathematically obscures the value of the savings.  If we framed the problem in terms of absolute savings, we would be better consumers.  But retailers know that saying "50% OFF!" attracts more attention than "$0.50 OFF!" in the sock department.  Likewise, car salesmen know that writing "$1000 BELOW INVOICE!" on the windshield looks a lot more attractive than "3% BELOW INVOICE!"