[SUPPLEMENTARY MATERIAL] How Rigorous Are Evaluations of Violent Extremism Prevention Programs? Results From a Systematic Methodological Review

SUPPLEMENTARY MATERIAL. The field of security studies, including the evaluation of Preventing/Countering Violent Extremism (P/CVE) programs, has encountered methodological challenges since its beginning. Notably, numerous gaps have been found in evaluating P/CVE programs, particularly in the approaches used for researching and analyzing collected data. This study systematically reviews the quality of 267 evaluations published in English, French, and Spanish up to December 2022, addressing concerns over bias and limited empirical evidence. Using the Mixed Methods Appraisal Tool (MMAT), we examined diverse study designs—including qualitative, quantitative descriptive, nonrandomized, randomized controlled trials, and mixed methods—to assess rigor and identify prevalent biases. While more than 70% of studies met most MMAT criteria—an encouraging outcome given initial low expectations—significant challenges remain. Only 17.2% employed control groups and 26% used repeated measures. In addition, deficiencies in transparency were evident: nonrandomized studies often failed to adequately manage confounding variables and describe sampling processes, and randomized trials provided limited details on their randomization procedures. Mixed-methods and qualitative studies, however, showed significant improvement in quality over time, contrasting with the relative stagnation of other designs. These findings underscore the need for more rigorous and standardized evaluation frameworks to enhance methodological transparency and reliability.