First operational definitions of independent, dependent, and extraneous variables defined keeping given hypothesis, Two conditions namely experimental, and controlled conditions are to be considered, For example, noise by electronic sound hammer is produced under experimental conditions while no noise under control conditions is required. Subjects perform twenty mathmetical problems under distraction (under experimental condition, the noise produced by sound hammer ), while the same problems are solved under calm and quiet conditions no noise ). Total time and errors committed by the experimental and control Ss are noted. Independent variable that is noise carefully manipulated under experimental condition while noise will be controlled. Compare results. Another example, stress produced under experimental conditions while no stress.Another example,effect of positive reward on mental work.Ss are directed that after work perfomce $20 will be gienen to Ss, while Ss perorm the same work without any reward .Also consider this example, high achievement oriented Ss perform work while same work performs low achievement oriented Ss.