Educational psychologists investigate the impact of different types of instruction on learning. in one study, researchers taught a math lesson to 9th-graders using the “inventing to prepare for learning (ipl)” instructional cycle. a second group of students received traditional “tell and practice” instruction. after the lessons, both groups studied a worked example of a math problem on their own. then they took a test that included problems like the worked example. the journal cognition and instruction published the results in 2004.pick the best description of this study: a. an observational study to make an estimate or a claim about a population b. an observational study of an association between two variables c. an experiment to establish a cause-and-effect relationship between two variables d. no answer text provided.