Dr. Low is interested in studying the effect mood has on the willingness to help a stranger. She randomly assigns half of her participants to the pleasant mood condition and shows them funny film clips. The other half of her participants is assigned to the unpleasant mood condition and is forced to watch boring film clips. She then gives every participant an opportunity to donate money to a homeless stranger. Dr. Low is using an design A. experimental
B. correlational
C. case study
D. repeated measures