Give difference between field experiment and …

In a true experiment, participants are randomly assigned to either the treatment or the control group, whereas they are not assigned randomly in a quasi-experiment. Randomized trials are experiments in which the division into treatment and control groups is determined at random (for example, by tossing a coin). ... In some cases, quasi-experiments also involve random assignment, such as in the lotteries sometimes used to distribute school vouchers. In a true experiment, each participant who volunteered would have an equal chance of being assigned to any of the three groups. Quasi-experiments are employed when the researcher is interested in independent variables that cannot be randomly assigned. Quasi-experimental research involves the manipulation of an independent variable without the random assignment of participants to conditions or orders of conditions. Among the important types are nonequivalent groups designs, pretest-posttest, and interrupted time-series designs.