The pain relief from placebos has never been explained

Why might people high in agreeableness tend to live longer?

a. They have a strong social support system of friends and loved ones. b. They tend to maintain good diets. c. They are less likely to be manipulated and controlled. d. They have stronger immune systems due to genetics.

In terms of assigning subjects to different treatment conditions, researchers should try to

a. recruit as few subjects as possible. b. make use of animal subjects as often as possible. c. make the number of subjects as similar as possible in all groups. d. deceive the subjects as much as possible in order to maintain high levels of accuracy.