An increasing degree of control is needed as studies move from descriptive or correlational to experimental designs. which of the following is true about control?
a. the degree of control will not influence the results of descriptive or correlational studies.
b. sample selection is not included as part of the control in a research study
c. control is needed to reduce the effects of confounding or extraneous variables on the variables being studied.
d. increasing control and rigor in a study ensures that outcomes will be as the researcher predicts

c. Control is needed to reduce the effects of confounding or extraneous variables on the variables being studied.      

Explanation:

A control is an observation or an experiment is designed to reduced the effects of the variables other than the independent variables. This will increase the reliability of the results. It also reduces the confounding effects on the various variable that is being studied.

Hence the correct option is (c).

answer; i believe the correct answer is (4) flip a coin as each participant arrives,heads indicates assignment to the first group: tails indicates assignment to the second group;

the answer is a wheel