What Is an Experimental Design

What is an experimental design?

A) A design in which the researcher can control the assignment of values on an independent variable to test its effect on a dependent variable
B) A design in which the researcher does not have control over the assignment of values within an independent variable
C) A design in which the observations included in the study are inherently similar to each other on a number of important dimensions so that variation in an independent variable can be used to explain variation in a dependent variable
D) A design in which the observations included in the study are very different from one another, but manifest the same value on the dependent variable under consideration