A researcher was interested in whether a new method of teaching fractions was more effective for student learning. She had an assistant randomly assign participants, who had no understanding of fractions, to either a new technique group or to an old technique group prior to testing. All participants then completed the same math test as a measure of their learning. In this scenario, neither the researcher nor the participants knew if they were assigned to the new technique group or the old technique group. This would be considered a _____ study. a. single-blind b. double-blind c. placebo d. poorly calibrated