Good but bittersweet news for fans of The Americans. The hit FX drama series, which focuses on Russian spies living undercover as Americans in the 1980s, is currently in its fourth season, with three more episodes to go, and FX has renewed the critically acclaimed show for not one but two more seasons!
Experiments that take advantage of natural occurrences are quasi-experiments, for example, comparing achievement level of first-born children with that of later-born children; or comparing student performance at two schools, one of which has a lower student-teacher ratio.
A type of quasi-experimental design that is generally better than either the nonequivalent groups design or the pretest-posttest design is one that combines elements of both. There is a treatment group that is given a pretest, receives a treatment, and then is given a posttest. Quasi-experimental research involves the manipulation of an independent variable without the random assignment of participants to conditions or orders of conditions. 2  Among the important types are nonequivalent groups designs, pretest-posttest, and interrupted time-series designs.