What is wrong the following conclusion? All students in North Carolina should take an online SAT course in order to help improve their score. This conclusion came from students at Mathville High school. All students at Mathville High school in North Carolina took an online SAT prep course. Their average increase in test scores after the course was 200 points. The conclusion cannot be trusted since offical scientists did not administer the online course. The conclusion should have been made for the entire United States not just the students in North Carolina. Their scores did not improve enough to say there was a difference. The sample was not a simple random sample.