thigger
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hi !!!
its my 1st time here in this forum....dont really know where to post my queries....my problem is a very simple n dumb one at the same time, i know u all might laugh but i cant interpret scores. my oasis was updated saying that my scores r on the way, i tried the oasis trick n found out that i have already passed...now i am just waiting for the score sheet....BUT.....i cant even understand what the scores mean !
i have heard ppl talk abt 3 digit n 2 digit scores very often but i have never been able to understand it. recently i asked some1 how to calculate percentiles, he replied...there r no precentiles in mle's...is this true ? but how could that be since i heard so many of my friend saying ...they got a 90 percent, a 92 percent or whatever ......help plz n be simple n kind as i am weak in maths ...thanx a bunch!
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| p53
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that's my favorite subject .
in your score report they will give you your 3-digit score, your 2-digit score, and Mean and Standard Deviation for recent US/Can registrants (not IMGs) - first time test takers.
it's common misconception to call 2-digit score percent or percentile - 2 totally different things, by the way; it's neither percent, nor percentile!
from biostatistics you should know that percentile is the percent of people from total 100% who received scores lower than yours.
by using your 3-digit score, Mean and Standard Deviation and special statistical table, you can calculate your percentile, and by using your 2-digit score, you can calculate appr. percent of correctly answered questions.
for more information, see
http://www.prep4usmle.com/forum/comments.php?id=3...
Edited by p53 on 04/21/06 - 04:46 PM
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| adeelmd
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getting a 98 is approximately being in the 86 percentile. correct me if i'm wrong
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where i lay my head is home.
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| thigger
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thanx p53 ....ur very helpful but i am very dumb 
i still cant understand any of this n ur links just confused me even more. i did not study bs properly n i dont know anything about curves n standrad deviations....can u plz explain by giving a particulat score example???
n if i still dont get it...i'll just post my scores here once i get them so that u can calculate my percentile for me, LOL
thanx again...ur far too kind !
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| p53
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thigger, I guess you should review chapter about Standard Deviation (SD) once again.
OK, here is an example adeelmd gave to us - 2-digit score 98, corresponding, if I'm correct, to the 3-digit scores 242 and 243.
mean and SD for the USMLE step 1 are 216 and 24, respectively; let's take our score - 242 - and take the mean from it: 242 - 216 is 26; this number shows to us how much higher (or lower) is our score than mean; now, let's divide this number by 1 SD - 26 : 24 is 1.08; this is z score; z score tells us by how many SDs is the given score higher or lower than the mean; using z score and statistical table for it we can calculate percentile; in this case, our z score is a bit more than 1 (1 SD / 1 SD is 1), so I can say even without the z table, that percentile in this case is a little more than 84, because I know that if you have got score that is 1 SD above of the mean, this means that 50% + 34%, i.e. appr. 84% of examinees have received scores lower than yours and only appr. 16% of them have received scores higher than yours; but let's see what will we get exactly for 1.08 z score - in z table it's said that this corresponds to the appr. 86th percentile, i.e. only 14% of examinees have received scores higher than this.
adeelmd was right.
Edited by p53 on 05/13/06 - 04:21 AM
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| thigger
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P53 thank-u very much for making it so easy.For so long i thought i would never be able to get hold of it ....
correct me if i am wrong ....taking another example....lets say some1 got a 3 digit score of 300. then we subtract 216 from 300 giving us 84...divide that 84 by 24...we get 3.5...next we just have to see what this 3.5 corresponds to in the z-table, that'll be our percentile...am i right ??
one more question....is the mean always 216 for step 1 ? n what about the SD...is it always 24 ? n where can i get a hold of the z-table ?
thanx again p53....i owe u one 
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| p53
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yes, that's right!
though theoretical score 300 is too high score for the USMLE - never have heard that someone has got it.
in recent score reports it's said that currently mean and SD for step 1 are 216 and 24, respectively, but this figures can be changed in the future - for example, if proficiency of examinee will rise, mean also will rise.
you can find z tables in most biostatisitics books.
Edited by p53 on 04/24/06 - 04:44 AM
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| thigger
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i am sorry that i keep bombarding u with my dumb problems.....i tried looking through a few statistic books for z tables...couldnt find it....searched google n got one z table but then i couldnt read it ...whats going on ? i feel so dumb ....
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| p53
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give me your link of the z table and I'll show you how to read it.
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| thigger
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hi again p53 !
i know u must be angry at me now for not understanding something every1 finds simple
i tried making some sense of the z-table with the 3 digit score....correct me if i am wrong plz....
232 = 75%
233 = 76%
233 or 234 = 77 %
234 or 235 = 78%
235 or 236 = 79%
236 or 237 =80%
237 or 238 =81 %
238 = 82 %
so on..n so on ....am i right ? n i dont understand the overlap between some percentages...for example...235 could be a 78 as well as a 79 %...whats up with that ?
thanx a lot for ur patience ...n r u one of the moderators ?
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| thigger
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http://www.prep4usmle.com/forum/comments.php?id=3...
r u online right now ?
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| thigger
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http://davidmlane.com/hyperstat/z_table.html
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| p53
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your calculations are correct (congratulations!), so I don't think that you need my help in reading z table.
these numbers are just rounded approximations, so there could be the overlap between some percentiles.
no, I'm not one of the Moderators - I'm just a Senior Member.
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| thigger
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thanx a bunch for ur patience 
i bet after all this drill with me...its not one of ur fav. subejcts anymore.
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| thigger
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dear p53 !
i think i am going to bother u again once i get my scores....u know, to have u interpret my scores since u seem to have such an authority on this subject..... i hope u dont mind ....
i thought u have to have atleast a 3 digit score of 232 to pass which equals 75 percent but i just read a post by some1 who got 216/88 n says he passed...i am lost again n feel like such a goat !
dont we need atleast a 75 percent to pass ?
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| p53
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what's the passing score for the USMLE step 1? it's 182 (3-digit score) or 75 (2-digit score). 75 is a 2 digit score - not percent!
question: what percent of questions you have to answer correctly to get passing 2-digit score 75?
answer: 60-70%, i.e. getting 75 corresponds to the answering 65(+/-5)% of questions correctly.
Edited by p53 on 04/22/06 - 08:39 AM
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| thigger
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this percentile business is so confusing, no wonder NBME ppl discontinued it...
so, coming back to the 2 digit score.... 75 in the minimum that u should score to pass n 99 is the max that u can score on a 2 digit score ? am i right ? n even though 98 on a 2 digit score sounds great but it is only 86 percent as u n adeelmd had said earlier ? so, does that mean that ppl have never scored higher than an 86 or an 87 percent in mle's ????
if this is all correct....then i think i would rather stick to the 2 digit scores since that sounds much more easier to interpret....
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| p53
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'75 in the minimum that u should score to pass n 99 is the max that u can score on a 2 digit score' - that's right.
98 on a 2 digit score is only 86th PERCENTILE (not percent) - to avoid confusion you should use the term 'percentile' in this case - otherwise people will think that you are talking about the percent of correctly answered questions, not about the percent of recent examinees who scored lower than you.
'does that mean that ppl have never scored higher than an 86 or an 87' PERCENTILE? -
no, it doesn't mean this - first of all, for the calculation of percentiles we are using 3-digit scores, not 2-digit ones; then, 2-digit score is 'frozen' at 99, but 3-digit score continues to rise even after 2-digit score has reached it's top maximum (i.e. 99) - so, we have lower 99s (the lowest 99 corresponds to the 3-digit score 244 or 245 on the USMLE step 1), and higher 99s - the highest (maximal) 3-digit score isn't defined for the USMLE.
The lowest 99 (244) corresponds to the 88th percentile - but the highest 99 someone has ever got corresponds to the 100th percentile - of course, if you have got the highest 3-digit score on the USMLE (the highest at that moment, not the highest possible - see
http://www.prep4usmle.com/forum/comments.php?id=2...) you are standing at the top of the list and all 100% of examinees (except yourself) have scored lower than you.
if you have got score that is 3 Standard Deviations above of the mean (i.e. currently, 99/288 for step 1), only 0.13% of US/Can first time examinees have received scores higher than yours, i.e. you are at the 99.87th percentile. Actually, I have never heard that someone has received such a high score, but there are members of this forum who are at the 99th percentile - see, for example, http://www.prep4usmle.com/forum/thread/32039.
yes, USMLE has discontinued to provide percentiles directly - http://www.usmle.org/Scores/percentiles.htm
- but actually they encourage its further use - otherwise, what's the meaning of providing the mean and standard deviation for recent first-time examinees from US and Canadian medical schools in every score report? by using 3-digit score, the mean and standard deviation and z table, everyone can calculate his/her percentile easily, like we did above;
you can stick to whatever you want - I just explained how the USMLE scoring system works.
Edited by p53 on 04/26/06 - 10:33 PM
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| thigger
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okkkk.... so, 182 passing 3 digit score, 75 passing 2 digit score which can be 99 max at a 3 digit score of 245 n freezes thereafter but the 3 digit score can keep rising....so, even if u have a 99, u might have a different percentile from some1 with another 99 as ur 3 digit scores can be different (which we use to calculate percentiles anyway )....ok...one question then, when we have low 99's as well as high 99's , then y do ppl wish each other a 99 ? y dont they say i wish u a high 99 ? sounds funny, i know...
n another wierd question....when we use only a 3 digit score to calculate percentiles (n so is done by the residency directors as u had mentioned ) then what is the use of a 2 digit score anyways when it freezes at 99 ??
thanx for explaining the difference between percent n percentile..percent is the gross percent of the questions u need to answer right in order to pass, roughly 60-70% n percentile is the percent of ppl u stand higher than ...am i right here ? i hope u get what i am trying to say ...
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| thigger
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p.s.
p53 i really liked the way u analyzed an's scores...would u plz do that for me too when i get my scores ?
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| p53
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yes, you got what I was trying to explain.
people actually wish each other high 99 when they are sure that someone is going to get 99.
differences between 99s make sense only if you are comparing people with 99s - it's like the highest league - only 12% (I mean step 1) of recent first-time examinees from US and Canadian medical schools are in this highest league - for IMGs this percent is much lower (though I don't know how much).
OK, buddy, first get your score report - though I think you can analyze it yourself now - that was my aim.
I wish you high 99.
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| thigger
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gracias
i think i must have barely passed as i didnt do brilliant on the exam....who cares ? i passed anyways , lol.
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| p53
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just now was reading how Dr. Brochert advertises his book 'USMLE Step 2 Secrets' on www.amazon.com - he says:
'Written by Dr. Brochert, who scored in the 99th percentile in Steps 1 and 2 of the U.S. Medical Licensing Exam (USMLE)...'
http://www.amazon.com/gp/product/156053608X/ref=s...
what do you think?
do you think he has got 272 on both step 1 and step 2 (this 3-digit score is required to reach 99th percentile on both steps) or do you think he just doesn't know that 2-digit score 99 doesn't mean percentile? ha-ha-ha
Edited by p53 on 04/26/06 - 10:05 PM
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| thigger
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i think it was a good publicity stunt 
i did not get my scores till now, they say it usually takes 2-3 days...i have been waiting for over a week now....this is so not right !
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| thigger
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dear p53 !
i got my scores 2 weeks ago...its horrible ....76! i mean, i knew that i had done bad but internally i was hoping for anything above 80 (human nature). i am so depressed cuz everywhere i look in this forum, i see geniuses with scores in their 90's...i feel so depressed !!! is every1 in this world so smart or have all the smart ppl gathered under this one roof ?? n have u honestly heard of any1 with a 76 b4 ? honestly , i never have...
Edited by Aashi on 05/14/07 - 04:02 PM
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