An experimenter is investigating the effects of noise on theperformance of a tracking task. The task is to use a mouse to keepa cursor on a computer screen on a randomly moving target dot. Thedependent variable is the amount of time a person can keep thecursor on the dot. It was hypothesized that subjects performing thetask when no environmental noise is present will keep the cursor onthe target for a greater amount of time than subjects who performthe task while listening to loud noise.

Each action by the experimenter that is described next confoundsthis experiment by letting an extraneous variable varysystematically with the independent variable of noise condition.For each action, identify the extraneous variable confounding theexperiment and explain why the experiment isconfounded.                                                                                   

3a. [1 point] The experimenter assigned ten 20-year-old males tothe no-noise condition and ten 60-year-old females to the noisecondition.

3b. [1 point] The experimenter urged the subjects in theno-noise condition to try very hard, but forgot to encourage thesubjects in the noise condition.

3c. [1 point] Subjects in the no-noise condition performed theexperiment at 9:00 A.M. and subjects in the noise conditionperformed the experiment at 4:00 P.M.

3d. [1 point] The experimenter let participants choose whichgroup (no-noise or noise condition) they wanted to be assignedto.