Just wondering.
They always curve such that the average raw score is 70 with a SD of 8.
That's not true -- when the exam was developed, the first group had their scores standardized to a mean of 70 and standard deviation of 8. However, it isn't curved for each group that takes it. The average now is several points higher for most shelf exams. Depending on the time of year, for instance, the Internal Medicine averages can range from 73 in the first quarter of the year to 76 in the fourth quarter. I don't have the specific numbers for the Family Medicine shelf, but I think it's a safe bet that the averages now for all the shelf exams are closer to 75 than 70.
Do you work for the NBME? Because they clearly state that the test is scaled to a mean of 70 with SD of 8.
Here are the national means given to us by our school for last year. From my understanding, these national means are compromised of 3rd year medical students who have takek the test as their last 3rd year shelf (ie. have completed all rotations in 3rd year and prior shelf exams).
FM: 72.7
IM: 76.0
OB/GYN: 72.9
Peds: 75.8
Psych: 76.7
Surg: 72.4
This sounds like a faulty measure and probably high suspect, statistically. There aren't enough people taking each one last to compare.
This is probably only for your school since the NBME does not have the data to provide these results.
The NBME average is scaled to a 70.
Read the link in my last post -- the NBME does actually have this data, and I'm betting that ChiDO's numbers are right on. The average of 70 and standard deviation of 8 are for the original group that they used to curve the scores. It doesn't get rescaled for every group that takes the test.
You are misreading the NBME information.
Just as they use old data to calculate your score on their Comprehensive examinations (Comprehensive Basic Science Self-Assessment (CBSSA)), which they compare to a similar cohort from the 1990s, they use the same formula to compare you to a group taking the shelfs.
How in the world does the NBME know what order each student takes his/her 3rd year rotations? It is different for almost every student, and varies between med schools.
The scores that ChiDo quotes are for people who took each shelf exam at the end of his/her one last in 3rd year. So, even within a class, it will vary from person to person.
Can you see what I mean?
You said ChiDO's numbers are just for his (or her) class only -- I highly doubt that. I'm guessing those are the fourth quarter (end of year) numbers published by the NBME for each shelf exam.
Apparently not. You said that the NBME average is scaled to 70 -- currently, that's not true. It was scaled to 70 for a group back in the 1990s, but it is not scaled for each group that takes the exam now and therefore has increased for all of the shelf exams.
You should really reread his post. He specifically stated that each average was based only on people who took that shelf exam as their last core shelf.
You seem to be proving my point..then suddenly creating imaginary data that is never stated on the NBME web site. There is nothing published by the NBME that states anything other than scaling the score to 70.