A researcher does a study of a curriculum on mass transit. She assigns a group of students from a rural school to receive the curriculum. She assigns a school in a major urban area to the comparison condition. She measures the results of a posttest on the curriculum. She finds that the groups score the same on the posttest. What can you conclude from this study? Group of answer choices We can say for sure that the curriculum does not improve knowledge of mass transit. There are no extraneous variables in this study. We can say for sure that the curriculum improves knowledge of mass transits. Rural versus urban location is an extraneous variable that makes it hard to draw a conclusion