A researcher who studies a fixed group of people over a long period of time is, by definition, using the ______ method

Tarpley and Schroeder attempted to reduce face-slapping in an 8-year-old boy by providing food when the boy played with a ball. The result was that face-slapping __________

a. decreased by 40% in two hours b. decreased by 60% in one hour c. decreased by 90% in 40 minutes d. increased by 50% in 20 minutes

Miscarriage usually stems from___________

a. the mother being a teenager b. the mother being over 40 years old c. the mother's use of tobacco d. abnormalities in the developmental process