A health psychologist conducts an experiment to test the effectiveness of four techniques for helping a person to relax. The psychologist has a limited number of people available to participate in the experiment and each relaxation technique takes some time to complete. The psychologist has decided, therefore, to use the incomplete repeated measures design with all possible orders to balance practice effects. What is the minimum number of participants the psychologist will need for this experiment?

An experiment can be explained as the testing of a hypothesis. In the experiment, an independent variable can be manipulated and the dependent variable could not be manipulated. The dependent variable could be measured and the extraneous variable could be controlled. The advantage of the experiment is that it is objective so the viewpoint of a researcher does not affect an experiment. So the date becomes more valid and reliable and not biased.

There are conducted three types of experiment :

Lab experiment

Field experiment

Natural experiment