perit-, perien-, peri-
(Latin: test, tested; try; experiment; risk, danger, dangerous, hazardous)
2. Dangerousness; danger; hazard; full of or involving peril.
A lack of control sometimes leaves quasi-experiments with doubtful outcomes because they often lack internally consistent logic, and someone can often find the potential for circular logic, and other invalid reasoning.Quasi-experiments with controversial outcomes almost always become embroiled in arguments over the lack of internal consistency.
A claim that scientists make for quasi-experiments is that they have external validity, by which they mean that the conclusions are widely applicable for the reason that they are drawn from a phenomenon as it exists in the field.