Problem
A researcher assessed exercise activity (in the form of wheel running) in a sample of rats before and after consuming an acute dose of caffeine, and predicted that caffeine would increase activity. Rats were provided with access to a running wheel for 1 hour before and after receiving a caffeinated solution, and the number of wheel revolutions was measured as a representation of exercise activity. Shortly after the rats consumed caffeine, the fire alarm went off in the testing room as part of an unannounced drill. Immediately after the alarm bells and lights stopped, the researcher gave the rats access to their second round of wheel running. The researcher found support for her hypothesis, with the rats running more after receiving caffeine than before receiving caffeine.
a) What is the independent variable and levels?
b) What is the dependent variable?