Independent variables are those that are manipulated by the researcher, dependent variables are those that are measured, and extraneous variables are those that are not controlled that could influence the dependent variable. Researchers attempt to control extraneous variables through random assignment and holding all variables constant except the independent variable. Levels of evidence range from expert opinion to randomized controlled trials, with stronger evidence able to lead to broader practice changes.

1. 1. A.Compare independent variables, B.dependent variables,
and C.extraneous variables. D.Describe two ways that
researchers attempt to control extraneous variables. E.Support
your answer with peer-reviewed articles.
2. A.Describe the "levels of evidence" B. and provide an
example of the type of practice change that could result from
each.