Educaton testing companies provide tutoring, class room learning and practice tests in an effort to help student to perfom better all tests such as the scholastic aptitude test{SAT}. the test preparation companies claim that their courses will improve SAT score performance by an average of 120 points{ thewall street journal January 23, 2003. a researcher is uncertain of this claim and beleves that 120 points may be an overestimate in an effort to encourage students to take the test preparation course. In an evaluation study of one test preparation service, the researcher collects SAT score data for 35 students who took the test preparation course and 48 students who did not take the course