The order of items above is the best order to present each part of the introduction: get the reader's attention, move toward the thesis statement, and then present the thesis statement. The thesis statement usually is most effective as just one sentence at the end of the introduction, so you should avoid presenting the thesis statement as the first sentence of the introduction and should avoid presenting the thesis statement in more than one sentence. (Information about thesis statements is presented on The Thesis Statement Web page.)
Experimental methods are used to demonstrate causal relationships between variables. In an experiment, the researcher systematically manipulates a variable of interest (known as the independent variable) and measures the effect on another variable (known as the dependent variable). Unlike correlational studies, which can only be used to determine if there is a relationship between two variables, experimental methods can be used to determine the actual nature of the relationship. That is to say that if changes in one variable actually cause another to change.