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.
Experiments can be done in the field or in a laboratory. They can involve human or animal subjects. What distinguishes the type of experiment is the degree to which the experimenter can assign subjects to conditions. Three types are described here: True, Quasi- and Single-subject experiments. In a true experiment, subjects are randomly assigned to the treatment conditions (levels of the independent variable). The only differences in the groups would be due to chance. True experiments are excellent for showing a cause-and-effect relationship.