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September 2020 Does terrorism trigger online hate speech? On the association of events and time series
Erik Scharwächter, Emmanuel Müller
Ann. Appl. Stat. 14(3): 1285-1303 (September 2020). DOI: 10.1214/20-AOAS1338


Hate speech is ubiquitous on the Web. Recently, the offline causes that contribute to online hate speech have received increasing attention. A recurring question is whether the occurrence of extreme events offline systematically triggers bursts of hate speech online, indicated by peaks in the volume of hateful social media posts. Formally, this question translates into measuring the association between a sparse event series and a time series. We propose a novel statistical methodology to measure, test and visualize the systematic association between rare events and peaks in a time series. In contrast to previous methods for causal inference or independence tests on time series, our approach focuses only on the timing of events and peaks and no other distributional characteristics. We follow the framework of event coincidence analysis (ECA) that was originally developed to correlate point processes. We formulate a discrete-time variant of ECA and derive all required distributions to enable analyses of peaks in time series with a special focus on serial dependencies and peaks over multiple thresholds. The analysis gives rise to a novel visualization of the association via quantile-trigger rate plots. We demonstrate the utility of our approach by analyzing whether Islamist terrorist attacks in Western Europe and North America systematically trigger bursts of hate speech and counter-hate speech on Twitter.


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Erik Scharwächter. Emmanuel Müller. "Does terrorism trigger online hate speech? On the association of events and time series." Ann. Appl. Stat. 14 (3) 1285 - 1303, September 2020.


Received: 1 February 2019; Revised: 1 December 2019; Published: September 2020
First available in Project Euclid: 18 September 2020

MathSciNet: MR4152133
Digital Object Identifier: 10.1214/20-AOAS1338

Keywords: Causal inference , event coincidence analysis , event series , event synchronization , hate speech , Independence test , social media , statistical association , terrorism , time series

Rights: Copyright © 2020 Institute of Mathematical Statistics


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Vol.14 • No. 3 • September 2020
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