A study tested the effects of sugar on hyperactivity in kids by randomly assigning kids to two groups, one that drank a sugary drink and another that drank an artificially sweetened drink, and measured the kids' levels of hyperactivity. The study found no difference in hyperactivity between the two groups of kids. (Note: The link between sugar and hyperactivity has been thoroughly disproven.) The independent variable is ______, while the dependent variable is ______