A researcher predicted that the presence of other people (the independent variable) leads to a decrease in math performance (the dependent variable). To test this prediction, the researcher had participants first complete a set of math problems while alone and then, the same participants completed a set of math problems with other people present. After each participant was tested in both conditions, the researcher compared the results. In this study, the researcher used a Group of answer choices Within-subject design. Between-group design. Variable- group design. Interval- group design