Clayton (1998) noted test takers gained an average of 6 to 12 points on the verbal section of the test and 13 to 26 points on the math portion of the test. An article in the Washington Post refers to a study of commercial test preparation courses by the National Association for College Admission Counseling that concluded that students who partook the course only improved by an average of 30 points (n=3492).

In 2016, the SAT format and scoring method changed. Khan Academy offered a free 20-hour SAT Practice. According to some research by the College Board (2017), the organization behind the SAT, studying for the SAT for 20 hours on free Official SAT Practice of Khan Academy is associated with an average score gain of 115 points. The average score gain is based on a sample of students who took the PSAT/NMSQT and then the SAT, and it may not reflect the true population of test takers.

After the Khan Academy course showed an average score increase of 115 points, some companies switched their position. Test-preparation organizations like Kaplan, Princeton Review, etc. advertised their services by claiming that students gain, overall, 100 or more points on the Scholastic Achievement Test (SAT).

According to a study by the National Association of College Admission Counseling (NACAC), SAT prep courses raised critical reading scores by about 10 points and math scores by about 20 points (Grove, 2019).

The 2017 report detailing the results of Khan Academy SAT test preparation has a sample size of approximately 250,000, average score increase 115 points, and 16,000 participants gained 200 or more points.

1. Assuming this data is normally distributed, what is the probability of 100 or more points?
2. Use 16,000 and 250,000 to compute the upper tail probability:
3. Use upper tail probability to compute Z score:
4. Use score to compute standard deviation:
5. Use mean and standard deviation to compute probability:
6. Do you think that taking one of the Kaplan, Princeton Review, etc. classes would give a test taker 100 or more points?
7. How might this be a biased statistic?

Sources:

Clayton, M. (1998). Does paid prep raise SAT scores? The Christian Science Monitor. Retrieved from https://www.csmonitor.com/1998/1208/120898.feat.feat.5.html#:~:text=Two%20of%20the%20biggest%20SAT,commissioned%20by%20the%20College%20Board.

College Board. (2017, May 8) New Data Links 20 Hours of Personalized Official SAT Practice on Khan Academy to 115-Point Average Score Gains on Redesigned SAT. https://newsroom.collegeboard.org/new-data-links-20-hours-personalized-official-sat-practice-khan-academy-115-point-average-score

Grove, A. (2019, May 1) Are SAT Prep Courses Worth the Cost?. https://www.thoughtco.com/are-sat-prep-courses-worth-the-cost-788672