Empirical Power Analysis of a Statistical Test to Quantify Gerrymandering

Fuente: arXiv
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Hauptverfasser: Clark, Ranthony A., Glenn, Susan, Lee, Harlin, Villar, Soledad
Format: Preprint
Veröffentlicht: 2025
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author Clark, Ranthony A.
Glenn, Susan
Lee, Harlin
Villar, Soledad
author_facet Clark, Ranthony A.
Glenn, Susan
Lee, Harlin
Villar, Soledad
contents Gerrymandering is a pervasive problem within the US political system. In the past decade, methods based on Markov Chain Monte Carlo (MCMC) sampling and statistical outlier tests have been proposed to quantify gerrymandering and were used as evidence in several high-profile legal cases. We perform an empirical power analysis of one such hypothesis test from Chikina et al (2020). We generate a family of biased North Carolina congressional district maps using the 2012 and 2016 presidential elections and assess under which conditions the outlier test fails to flag them at the specified Type I error level. The power of the outlier test is found to be relatively stable across political parties, election years, lengths of the MCMC chain and effect sizes. The main effect on the power of the test is shown to be the choice of the bias metric. This is the first work that computationally verifies the power of statistical tests used in gerrymandering cases.
format Preprint
id arxiv_https___arxiv_org_abs_2501_05761
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Empirical Power Analysis of a Statistical Test to Quantify Gerrymandering
Clark, Ranthony A.
Glenn, Susan
Lee, Harlin
Villar, Soledad
Computers and Society
Applications
Gerrymandering is a pervasive problem within the US political system. In the past decade, methods based on Markov Chain Monte Carlo (MCMC) sampling and statistical outlier tests have been proposed to quantify gerrymandering and were used as evidence in several high-profile legal cases. We perform an empirical power analysis of one such hypothesis test from Chikina et al (2020). We generate a family of biased North Carolina congressional district maps using the 2012 and 2016 presidential elections and assess under which conditions the outlier test fails to flag them at the specified Type I error level. The power of the outlier test is found to be relatively stable across political parties, election years, lengths of the MCMC chain and effect sizes. The main effect on the power of the test is shown to be the choice of the bias metric. This is the first work that computationally verifies the power of statistical tests used in gerrymandering cases.
title Empirical Power Analysis of a Statistical Test to Quantify Gerrymandering
topic Computers and Society
Applications
url https://arxiv.org/abs/2501.05761