________ means that there is a relationship between two or more variables.

Herbal remedies are __________

a) rarely subjected to placebo-controlled effectiveness studies. b) more effective than many prescription medications. c) regulated by the same government agency that regulates prescription drugs. d) generally ineffective for most problems.

Adolescents' circadian rhythms are in a

A) early wake phase. B) delayed phase preference. C) lack of sleep preference. D) decreased alertness phase.