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Hi all, I am posting this because i have see many people trying to correlate their scores like the NBME, UW, NBME offline and getting confused with some formulas and stuff.

first a quick review of USMLE scores: as many of you know the 2 digit score is not a percentage, not a percentile is just a scale... just imagine you have a ruler with 99 digits on it, and you are trying to measure something, the top digit always will be 99 and if the measure is higher you will say its above 99. So 2 digit score = a scale for quick assessing the score like ok this guy is above the mean (>95+) or this guy is below the mean (<85) or hes just at the mean (90...).

The 3 digit score is same as above just a scale but a more precise one, imagine now that your ruler have more than 286 digits (the higher score i know), now you can compare more precisely 2 guys above the mean or so. ie this guy is above the mean but he scored lower than this other guy.

ok now to business: i will start with the most famous, NBME this are very easy to correlate because they give you a scale from 200 to 800 (i think) and they give you the conversion table to the 3 digit score in the USMLE scale, the problem is when people take more than 1 and start saying, ok for me the most accurate was the form 2, or form 4 or what ever. ok first thing you got to remember here is that your trying to assess your performance in a 350+ question exam with 200 question exam, you should know that in statics the bigger the sample the most accurate correlation, and also you should remember that this values always have a confidence intervals so the score you get its a +/- correlation from the real score.
ok so why we score so differently in the NBME??? the real deal is THE LEVEL OF YOUR PREPARATION, what do i mean with this is, if you just have started your preparation for the exam and you take an assessment for most people the score will be lower that after the full 4 month preparation, also this means if you take 3 NBME in a row with a little or no studying in between your score will be the same in all 3 exams (remember i mean the same, within the confidence interval). so if you take a NBME form today you should put emphasis in the subjects you got wrong and after some serious time studying you should take another one to "assess your level of preparation". I have to add here that i have seen that most forms are very accurate for assessment but it seems that form 1 for step 2ck and step 1 is at the upper bottom of the confidence interval (it means that most people with same level of preparation score a little higher here) and form 3 of step 2 ck is at the bottom of the interval. so if you feel well prepared for exam and want to boost mood just take the form 1 at the last moment! smiling face (i just did that)

NBME offline: well the problem here is that we don't have the corrects answers, so is difficult to have a precise correlation but if you look for the answers in books or so you will find that its very close to the real online thing, so the first thing you should do is finish the test, and calculate your percentage, lets say 150/200 so you got a 75%, next you go to the magic table i attached here, and find the percentage there and look up for the 3 digit score!!, i don't know who did this table but is very very very accurate, i have tried it my self with 3 forms (step 2 ck) and it was almost the same score, you may ask, is possible to estimate your score with a percentage because all NBME forms are tested questions so they have the same level of difficulty. that's why the second we click on finish we have a score waiting for us, i am speculating here but they may use a table like this!!!! you ask, ey man but why they don't do this with the real deal??? i think this is because even if they have tested questions on the exam they also compare it to another test takers in the same period as you, so they have to wait 3 full weeks to make the comparison more accurate, in the score report they say: "This score is determined by your overall performance. for recent administration..." also "This profile should not be compared to those from other Step 2 CK administration".

Usmle World: this is very easy too, with the magic table. When we don't have the same level of difficulty when comparing two tests we use the percentile because the percentile as all of you know stats how well you did comparing to your other peers, lets say you got a 80% in a exam but with a 50 percentile and in another exam you got 60% with 85 percentile, in which exam you scored better? of course in the second one because in the first one you got a lot of corrects answers but you were just like other people taking the exam just in the mean (50th) but in the other exam you were above 85 percent (yes percent) of the people who took the exam. The Usmle World gives you a percentile!!! so you find your percentile and look up in our magic table and there you go!!!! REMEMBER!! if you finish your Usmle world 1 month after your exam and you keep studying your weakest subjects the most probable thing is that you'll be score higher than the calculated score because you increased your LEVEL OF PREPARATION. also if you stopped studying after the UW is probable that your score will be lower!, if you take it the day after you finish your UW is very likely that you be close to the calculated score because the percentile is the best way to compare two tests with different levels of difficulties... for me i finished UW 1 week before and my percentile was 78th in the table my score was 236/99 after that i studied harder and my final score was 243/99. so it was very close but a little higher...

Kaplan: for me its impossible to accurate estimate using kaplan's because i dint do it and because they don't give you a percentile, and we cant calculate the percentage because its not at the same level of difficulty, but if you still want to estimate anyway i do recommend using this link: or this one:

so which method is better estimator? the one that you did just before the exam! because the days before the exam you will have the same "level of preparation" (i do say this a lot.. .grin)

After all remember this is an estimation in statics nothing is 100% guaranteed, also if you freak outshocked, loose confidenceshaking head, get nervous rolling eyesor feel tired because you didn't sleep the last nightconfused, your performance on the exam could be a little lower, but if you do the exact opposite! you will ace!!!.nod

Good luck to everyone, fell free to open a discussion!!!

Attached Files:
NBME-SCORE-DATA.pdf (31 KB, 2881 downloads)

Edited by VQmismatch on Oct 21, 2009 - 5:27 AM


thank u..


WOW! and Thanks! Very well explained- and sooo important for peace of mind! I must confess -i am not very comp.savvy, neither did i know abt the forums much- generally family life, a very active and comp-literate husband and middle age kept me out of this loop- but thanks to a SP, i got to scout these places and am amazed at how useful, supportive, and informative the forums are.


Based on my experience with step 1, all I can say is that this table is accurate. After step 1, I was sure of 70% of questions, plus 20-25% of the remaining would be a right guess, because i made an educated guess every time i wasn't sure of the answer or i selected C when the subject was unknown to me. So approximately 77% of my anwers were right answers: I got a 90/218 on the score report. Based on that prediction, my Ck result would be ... I won't say, I'm kind of superstitious, so let's wait for the score...

Edited by papio on Mar 21, 2009 - 6:05 AM


No prob friends hope you understand my brute english!... IMG

Papio i didn't understand, sorry.


wow, that was grtttttttttttttt...


VQmismatch, thanks for the very extensive explanation. Based on your experience, then, I gather it would be best to take the exam after reading the notes and IMMEDIATELY (or soon after) completing USMLEWorld because of the following reasons:

1. level of mental preparation is the same (it should be high and intensive at that point of review already, right? mental agility should be sharpened at this point)

2. score will be most similar to Uworld, if not higher (if given some more time to study the subjects in which one scored poorly)

In my case, I plan to allot twelve days to recap everything after my 30-day Uworld subscription. I hope that time period would be enough to master the subjects in which I didn't excel at and make my score even higher than what I got in UWorld.

What do you think of my plan? smiling face

Great post. Thanks wink

By the way, I checked the NBME practice exams and I'm a little confused. The USD 45 they charge is for one form only or for all the forms already? Thanks and God bless us all!

Happy weekend!


hi HGPRTase!

What i mean by this is not to do the exam right after the UW, i just say the more you study the higher the score you get, many people do the UW more than 1, (i did it 2 times complete and a third time wrong questions) so if you take the exam just after finishing UW the score may correlate, and may be very similar to the last blocks you did. But i have read that many people with score of 55% on UW have scored 99+ on the exam because they have revised the material over and over and they have increased their level... so my advice is to study, take NBME (45 dollar each with no answers) or UW self assessment (30 dollar with answers) and if you feel comfortable with the score then take the exam... if not keep increasing your level.

hope this helps!


Thanks for your answering my query, very good suggestions, VQ! nod I might take the UW self-assessment instead because of a limited budget.

I have some more concerns that don't relate to statistics anymore but I hope anyone of you might be able to address (I'll make a new post after this, don't kill me for digressing a bit grin):

1. I alloted 12 days for study between the end of UW and the actual exam -- do you think this is a very short time to master the subjects in which I did poorly? I planned this schedule so that my mind will already be agile for the actual exam as compared to let's say, a 30-day interval of review, then exam. In some old post, I remember Arlete suggesting 20 days to recap.

2. By the way, is there a particularly effective way to use UWorld? In Step 1, I just used mixed-timed and all-wrong answers for one month and then took the exam 5 days later. I got 55% in it and eventually got 201/82 in the actual exam. For the CK, I plan to do it subject-wise, then all wrong, then mixed mode. Any suggestions?

Happy weekend, you all smiling face



about the item number 1 i think what ever works for you is the best thing, but i must say if you get less than 60% in the UW you most take your time to analyze those subjects very well and the best thing to assess is to take a pre test using NMBE or UW until you get a desirable score, remember always the confidence interval...

about item number two i think ill post my experience of how to use UW but many people do many things, pick something you feel comfortable with...


Okay, thanks for your help VQ! smiling face I'm eagerly awaiting your post on using UW. grin Happy Sunday!


OK, Guys, just a single question.
That correlation is only when have finished UW all?
I guess...
Because I started it recently, I mean, I have done like 10-11 blocks and still have like 1800 question to do...

the correlation is at the end right? or what?



hello neurologox! you can do the correlation when ever you want!!!, but remember 2 things:

1- the most questions you do the more accurate is the correlation, it will be at best when you finish it...
2- if you start doing questions and you see your percentile, that should give you an idea of your level of preparation at that exact time, i mean if you take the exam right away. You will see that when you become familiarize with the questions and begin to improve your knowledge using UW your percentile will go up!

hope you understand me! see you later...


thank u very accurate i got 99/238 in step 1 and 99/255 in step 2 and the NBME seems to correlate well


I had 590/238 on NBME form 2 three weeks before exam.

Does that mean I can expect 95+?


hello papio,

Yes this means that you have achieved a level of 99 (or some where near), now is up to you to stay at this level and get even a better score (by keep studying and emphasis on your weakest areas) or just stop studying and get a lower score than that... it all depends on what you do in this three following weeks before the exam...

Hope this helps


hi VQmismatch,
Thank so much for your post;it is perfect!But i have a little question;
How do you understand that 78% percentile in UW equal to 236/99?
thanks so much!


Guys... this is sad... 2 weeks to take the exam (rescheduled already) and my percentile is NOT improving... may questions that I really don't know having reviewed kaplan yellow books and other questions that I failed like a stupid.

I will continue doing many blocks as I can to try to complete all the UW, but when the percentile does not improve is so worrisome.

I'd really appreciated it!


overal correct: 55%
percentile 31st


Hello Guys

Class09 you have to download the Table i attached in this post, then find out your percentile on the table, and check out the other numbers around your percentile...

Neurolox: hello man, how are you???? you must fight!! that's my answer to you, the only weapon we got against this is our brain and heart, just give your best! and you'll see it will improve.... well another thing is ill post something about "how to use UW" maybe you can find some help in that post... (i said that in a few posts ups, but i haven't got much time to do it sorry).

Edited by VQmismatch on Apr 12, 2009 - 7:42 AM

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