Quasi-experimental design

An experimental design that involves periodic measurements on the dependent variable for a group of test units. Then the researcher administers the treatment. After the treatment, periodic measurements are continued in order to determine the treatment effect. This is also called time series design. Such designs are useful because they can be useful in cases when true experimental designs cannot, and because they are quicker and less expensive. However, because full experimental control is lacking the researcher must take into account, the specific variables that are not controlled.