Dr. Walsh manipulates an independent variable and randomly assigns participants to different groups in order to study the effects on a dependent variable. This is an example of a (n) Multiple Choice

1. experimental design.

2. correlational design.

3. variable design.

4. scientific method.

1). Experimental design.

Explanation:

Experimental design is demonstrated as the research method that primarily intends to observe or evaluate the changes occurred due to the manipulation or controlling of an independent variable in the dependent variable. Such a research is chiefly inclined towards testing the various conditions in order to determine the association between the variables and the impact of independent variable over the dependent. Thus, Dr. Walsh's manipulation of an independent variable to examine its impact or effects on the dependent variable exemplify 'experimental research design'. Therefore, option 1 is the correct answer.