A study that has most of the characteristics of trying new methods to determine the accuracy of something, but which is unable to control potential factors, or perhaps is not guided by an idea of what all the factors are: Quasi experiments are similar to real investigations in that there are subjects, treatment, etc.; but it uses nonrandomized groups.

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.