A researcher studies a new mathematics program. At the beginning of the year, 100 students are randomly assigned to receive a new program and 100 students are randomly assigned to use the previously used mathematics program. The participants are pretested at the beginning of the year, and they are posttested at the end. What kind of experimental design did the researcher use? Group of answer choices pretest-posttest control-group design posttest-only design with nonequivalent groups one-group posttest-only design posttest-only control-group design