Child eyewitness researchers often bin age: Prevalence of the practice and recommendations for analyzing developmental trends.

Effective practices for eliciting and analyzing children's eyewitness reports rely on accurate conclusions about age differences in how children retain information and respond to memory probes. Binning, which is the practice of categorizing continuous variables into discrete groups, can lower studies' power to detect age differences and, in some situations, produce significant but spurious effects. In this article, we (a) describe a systematic review that estimated the frequency of binning age in child eyewitness studies, (b) analyze real and simulated data to illustrate how binning can distort conclusions about age and covariate effects, and (c) demonstrate best practices for analyzing and reporting age trends.