In an experimental study on the effects of sleep deprivation on depression, the number of hours that a participant stays awake is represented by the
a. random variable. b. independent variable. c. dependent variable. d. control variable.

The number of hours a participant stays awake is the independent variable of the study. This study would require the amount of sleep to be controlled and changed by the experimenters in order to view the changes in effects. This is the definition of an independent variable.

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;

i honestly speaking this is too long