Quasi-experimental research designs, like experimental designs, test causal hypotheses. In both experimental (i.e., randomized controlled trials or RCTs) and quasi-experimental designs, the programme or policy is viewed as an ‘intervention’ in which a treatment – comprising the elements of the programme/policy being evaluated – is tested for how well it achieves its objectives, as measured by a prespecified set of indicators (see Brief No. 7, Randomized Controlled Trials). A quasi-experimental design by definition lacks random assignment, however. Assignment to conditions (treatment versus no treatment or comparison) is by means of self-selection (by which participants choose treatment for themselves) or administrator selection (e.g., by officials, teachers, policymakers and so on) or both of these routes.