To test this hypothesis, the admissions counselors select a random sample of first year students and compare their scores on the SAT with those of the population of upperclassmen. They find that the first years do in fact have a higher mean SAT score. However, they are unaware that the sample of first years was not representative of all first years at Brainy University. In fact, the sample overrepresented those with high scores and underrepresented those with low scores.

What type of error ( Type I or Type II) did the counselors make?