Each study was classified as a randomised controlled trial (RCT), quasi-experiment (QE) or observational (Obs).
In anticipation of few randomised trials being found, studies in categories 1) and 2) were not restricted by methodology: randomised controlled trials and also natural experiments with pre- and post- comparisons and natural experiments with parallel groups were eligible for inclusion.
Randomised controlled trials (RCTs) are planned experiments, involving the random assignment of participants to interventions, and are seen as the gold standard of study designs to evaluate the effectiveness of a treatment in medical research in humans [11].
Natural experiments have a number of advantages over randomised controlled trials in health service research.
It's best to see experimentation as a continuum, ranging from the messiness of attempts to try something new to experiments using the best available social science, such as randomised controlled trials.
Randomised controlled trials, staggered enrolment trials, stepped-wedged trials, quasi-randomised trials, quasi-experimental trials and natural experiments will be included.
Limited or no evidence is available from randomised controlled trials.
There have been positive early results in randomised controlled trials.
Was there a controlled experiment?
It's about saving the world, one randomised controlled test at a time".
