Only four of the 75 studies drew representative samples.

Evidence

The reviewed studies were conducted in more than 50 different countries across the globe, including Europe, the Middle East, South East Asia, Oceania, North America, South America, and Africa. With 15 studies, the USA was represented most, followed by Spain (n = 10). The studies were conducted among a variety of sample populations, including members of ethnic or religious minority groups (n = 33), members of ethnic majority groups (n = 12), university students (n = 18), adolescents and young adults (n = 8), individuals recruited through online crowdsourcing companies, such as Amazon Mechanical Turk (n = 13), members of social media groups (n = 6), individuals with specific political affiliations (n = 8), terrorist suspects (n = 3), terrorist detainees (n = 2), and football hooligans (n = 1). Overall, the sample sizes were sufficient, with an average of 584 participants per study. Only six studies had small sample sizes with between 26 and 66 participants, due to limited access to the sample population (i.e. football hooligans, terrorist suspects or detainees). The average age per sample ranged from 15 to 46 years and the majority of samples consisted between 40 to 60% of men. In twenty studies (mostly involving university students), the sample consisted to more than 60% of females, while in only 12 studies (mostly involving terrorist suspects, individuals convicted for terrorism, members of religious communities, or football hooligans), more than 60% of the sample was male. Only four studies reportedly drew and examined representative samples. — Lea Echelmeyer, Anne-Marie Slotboom, and Frank Weerman, The Putative Effect of Identity on…, 49

Categorization

• QUESTION: Representativeness of only ~5% of studies is a severe external-validity constraint worth checking against the aggregate conclusion about the negative-identity mechanism.
• XREF: Cross-references concerns about convenience sampling (MTurk, student) in quantitative radicalization research framing the whole review.

Related

• Despite theory treating radicalization as a process, most quantitative studies are cross-sectional (similarity 0.81)
• Experimental and longitudinal designs are rare in quantitative radicalization research. (similarity 0.78)
• Personal-developmental identity processes remain nearly untested in quantitative radicalization research (similarity 0.78)