What is a quasi-experimental design? How is it different from an ex post facto design? Describe one weakness of the quasi-experimental design. Solution A quasi experiment is simply defined as nota true experiment. Since the main component of a true experiment is randomly assigned group this means a quasi experiment does not have randomly assigned groups. Ex facto designs are different from quasi experimental design as ex facto groups do not have random assignment. The study groups may provude weaker evidence because of the lack of randomness. Randomness broadens results to give better representation of the whole population..