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:

Group of answer choices

an observational study to make an estimate or a claim about a population

an observational study of an association between two variables.

an experiment to establish a cause-and-effect relationship between two variables