Originally Posted by Guile
I'm not sure why that is the case if the average is set to be 70 and the SD 8 for each testing. Wouldn't that lock in the percentiles? I think that it just means that an 80 late in the year means more than an 80 early in the year.
The reason the percentiles aren't "locked in" is because the exam isn't standardized to a mean of 70/standard deviation of 8 for each testing. Those numbers are based on, as the NBME puts it, "a scaling group of first-time takers from U.S. LCME-accredited medical schools who took this examination as a final clerkship examination under standard testing conditions." According to the NBME website, that group took the exam during the 1993-94 academic year. Presumably, like USMLE scores, students' shelf scores are increasing as schools admit more competitive applicants and students study more.