ABSTRACT
The purpose of experimental design is to test a hypothesis regarding some cause-and-effect relationship. In contrast to descriptive design, which aims to describe, experimental design seeks to explain. The experimental design is just opposite of exploratory design, used for very little information. An experimental design is appropriate when there's a great deal of knowledge, formulate a hypothesis and manipulate whatever one believe to be a cause to examine its effect, and one can control who does or does not get subjected to that cause. A cause refers to something that one can manipulate in such a way as to impose it on or offer to others. An effect occurs as a result of a cause. Three criteria for showing causation are that cause and effect must co-vary, that cause precedes effect, and that there are no other plausible alternative explanations for post-test differences. A control group is not subjected to or offered the cause.
