ACT to MCAT correspondence logic

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Rhino1000

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I just want to know if my logic sounds generally strong. My actual correspondence table isn't thought by me to be very accurate, because I did this roughly and with very little regard for detail, such as accurate standard deviations, and other things.

So according to: http://www.assessmentpsychology.com/iq.htm (sorry, it's the only site where I could find this information), the average physician "has" an ACT score of 27. If you look under the first table, you'll see that it comes from some source of the year 1972. The first table indicates that the average M.D. physician has (did have) an iq of 125, which is how they were able to determine that the average ACT of physicians was 27. If we try to look for old MCAT data, we see that only data as far back as 2002 is shown. The average MCAT for matriculants in that year is 29.6, and that average steadily increases each year until 2013, where it hit 31.3. This indicates an increase in average MCAT scores of medical students (and therefore physicians). Therefore, if we move backward in time from 2013, we see steadily decreasing ACT scores. If we extrapolate that trend to try to predict average MCAT scores for matriculants in 1972, we will find that it is very close to 25. But let's be generous, and say that average MCAT scores for students of that time was about 29.0, which is .6 points lower than the MCAT score of the students of 2002 (rather than closer to 5 points less, which is what line extrapolation would predict).

Then we will find that an MCAT score of 29.0 (the score of the average soon-to-be physician in 1972) corresponds to an ACT score of 27 (the ACT score of the average physician in 1972, according to the data on the given website). The standard deviation for the MCAT is 6.4, and the standard deviation for the ACT is 5.2 . We find that 2013 had a 2.1 point increase in average MCAT scores (for matriculants) compared to 1972, where we assumed that the average medical student scored a 29, so therefore we should expect approximately a 2.1*5.2/6.4 = 1.7 ACT point increase compared to that time. So the average modern medical student would then be expected to have an ACT score of 28.7.

The reason that I say that we should estimate that the physicians of 1972 wouldn't have an average MCAT score of 25, as the extrapolation would predict, is because that would predict an average ACT score for modern medical students to be about 33, which we know is simply not true. Also, that would be saying that the average physician would have an average MCAT score, which is also simply not true. So I am simply making the assumption that the MCAT scores of that time would be lower than students of 2002, but not as much lower as a simple extrapolation would expect.

And if the average modern medical student has an ACT score of 28.9, and the average modern medical student has an average MCAT score of 31.1, then then a 28.9 ACT score can roughly correspond to a 31.1 MCAT score. And to determine further ACT score/ MCAT score correspondences, we would simply add however much standard deviations we want to each score. E.g. the ACT STDV = 5.2, and the MCAT STDV is 6.4, therefore if we wanted to see how much one standard deviation below the average MCAT corresponds to as far as ACTs, we would simply subtract 6.4 from the reference MCAT score (31.1) and compare that to the reference ACT score of 28.9, minus its standard deviation (5.2). So then a 24.7 MCAT would correspond to a 23.7 ACT score.


TL;DR

The whole premise behind this very rough, possibly reckless analysis is that if we can find the average ACT of a modern medical student, then we can roughly assume that that average ACT score corresponds to the average MCAT of today's matriculants, and to find other corresponding scores, we would simply add the same number of respective standard deviations to each score. So if an average MCAT is 31.1, which corresponds to an ACT of 28.7, we can simply add multiples of 6.4 (the MCAT's supposed standard deviation) to the MCAT, and add the same multiples of 5.2 (the supposed standard deviation of the ACT) to the ACT score.

So: 31.1+6.4*x MCAT score ~=~ 28.7+5.2*x ACT score (where the x is the same number).
Or alternatively (if we find that I was using incorrect standard deviations, and/or incorrect estimates of current medical matriculant ACT averages):
Average MCAT (m. matriculant) + (STDV of MCAT)*x ~=~ Average ACT (m. matriculant) + (STDV of ACT test)*x
where x is the same value for both sides of the equation, and ~=~ here means "corresponds to"

This is consistent with the conjecture that the following correspondences are roughly accurate:

In short:
ACT MCAT
5.2 6.4 (standard deviations)
24.4 ~ 25.8
25.7 ~ 27.4
27.0 ~ 29.0
28.7 ~ 31.1
30.0 ~ 32.7
31.3 ~ 34.3
32.6 ~ 35.9
33.9 ~ 37.5
35.2 ~ 39.1
36.5 ~ 40.7

If by whatever extravagant methods, we find that the average ACT of modern medical students should be estimated to be 28.2 instead of 28.7, all we would have to do is subtract each of the numbers in the left hand column by .5, while leaving the corresponding MCAT scores the same (assuming standard deviations are correct). If other problems are found, an error in one of the numbers used in the bolded equation seems likely to be the source.

****
Assumptions:
-both score sets follow a bell curve, or are similarly skewed in score distribution.
-standard deviations are consistent across the entire range of possible scores for each test.
-MCAT scores of past medical students are lower than those of today's
-MCAT scores of past medical students are higher than expected from a simple line extrapolation from recent years score data.
-the early-mentioned website gave accurate numbers, (ACT of physicians in 1972 = 27, etc.)
-others that I can't recall
-others that I didn't even consider
-etc.


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Alternative method, using same basis of 27 ACT ~ 29 ACT
This uses the data sheet found at http://www.act.org/newsroom/data/2012/pdf/profile/National2012.pdf
The method:
In a nutshell: (# of people scoring ABOVE the given ACT score + 1/2*# of people scoring AT the given ACT score)/(Total # of People whose data was included in sample). This gives the decimal fraction of the people who scored higher than the average person with a given ACT score. I did this for every ACT score. I used the percentile of the basis 27 ACT (85.27) and corresponded that to the MCAT of 29 (percentile: 72.4). Then to find additional MCAT correspondences, I used the ratio of the # of people scoring higher than the average person with a given ACT score divided by the # of people scoring above a point below that score, and multiplied this ratio by the % of MCAT people who would have scored better than the equivalent.

Concrete example:
ACT 27 = MCAT 29
# of people scoring higher than a given person with a 27 ACT? This is equal to the number of people who scored a 28 + 29 + 30 + 31 +32 +33 +34 +35 + 36 + 1/2* the number of people who scored 27. (this is because half of the people who scored a 27 should be assumed to be slightly better than a 27, and the other half slightly worse, hopefully you know what I'm saying). Now divide this sum by the total number of people in the sample. We'll call this percentage "x". Now, the number of people who scored higher than a 28 is the number of people who scored a 29 + 30 +...+36 + 1/2*number of people who scored 28. Divide this sum by the total number of people in the sample, and we'll call this decimal percentage "y". Therefore the ratio of rarities of y to x is y/x. Well, we know that y/x*x gives you y. And we also know that 1-x (which is the ACT percentile) corresponds to some corresponding MCAT percentile we'll call z (which is the MCAT percentile of those who scored 29 on their MCAT in this case). We can say that the percent of people ("decimal percentage") of those scoring above that corresponding MCAT score is 1-z, and it corresponds to the percent of people scoring above it's associated ACT score, which we defined to be "x." Therefore x~1-z therefore just as y/x *x gives the percent of people scoring above a 27 on their ACT, y/x*(1-z) gives the corresponding percent of people taking the MCAT who would score above 28 ACT.

In a word: if one ACT score is 10 times rarer than a previous ACT score, then one's equivalent MCAT score should be 10 times rarer than the previous corresponding MCAT score. If we go from 85th percentile to 98.5th percentile on ACT, we should go from 72nd to 97.2nd on the MCAT.

Too long; didn't read?

Here is a table showing the end results (The second table is same as the one shown above). Notice the consistency between the two methods' results, except a slight discrepancy at the very top scores:

Updatedpercentile_zps7087e424.jpg


According to data collected from these two threads (I don't know if this is reliable, considering a huge likelihood that there is some sort of bias of those who chose to post their respective scores or not), these tables underpredict your MCAT by almost exactly one point:
http://forums.studentdoctor.net/threads/act-score-and-mcat-score-correlation.526626/
http://forums.studentdoctor.net/threads/act-vs-mcat.289029/

Therefore a table more consistent with that good/bad set of data may look more like:
ACT MCAT
36 42
35 40
34 39
33 38
32 36
31 35
30 34
29 32
28 31
27 30


Which also may suggest that the average incoming medical student scored 28 on their ACT. But again, that is based off of a change in results due to a potentially biased thread (coming from a MCAT study forum).

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Want to use the tables, but did not take the ACT, or certain circumstances rendered your SAT score more representative? Convert SAT to ACT here: http://www.act.org/solutions/college-career-readiness/compare-act-sat/.

Comment if you think I made a poor assumption regarding some of this. Including whether a 27 ACT should correspond to 29 MCAT, whether you think perhaps one of the two populations would have a larger standard deviation that should in no way correspond to the standard deviation of the other population, etc.

Edit: Changed the word "would" to the word "may" right before the last table.
 
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Alright guys, if no one is going to comment on my methods, then feel free to list your ACT scores and what you scored on the MCAT or at least on your practice exams. If your scores are not within 3 points of the predicted score in the table, list any causes of discrepancies. E.g. maybe you had really weird circumstances when you took the MCAT, etc. I personally think that the table will be generally accurate for people who were at least semi-serious students in middle school and high school, etc., and most discrepancies will come from a change in work ethic between the middle/high school atmosphere compared to college, or some sort of weird circumstances.
 
i havent taken the mcat yet but i hope this isn't true lol
my worse section on the act was the science reasoning section and the mcat is practically 2 sections of that + a critical reading section from sat ToT
 
Made comparison with about 51 samples from 2 threads of people listing their respective scores. Created additional table reflecting changes the data suggests should be made. May or may not be a change for the better depending on if that data is representative or not. Post updated.
 
I never took the ACT, but I got a 2190 on the SAT, and I am now averaging 33 on AAMC FL...Will let you know how I do on the real thing.

By the way, I wish you had done this with SAT instead of ACT. SAT is way more popular and ubiquitous.
 
I'm skeptical of any such comparisons since they test such different things.

ACT any random person off the street can take it and do okay. That means like if you are smart, you can expect to score reasonably well (even without preparation).

For MCAT, you can take a smart person off the street but they might fail because they never took the prereqs.

And even for those people who have taken the prereqs (AND prepared), it's still hard to compare.

I know that if you told me to take the ACT today, next week, next month, or a year from now, my score would more or less be the same. Same would apply for SAT.

For MCAT, my score would decrease (I finished studying for MCAT in the summer) as I rapidly forget stuff.
 
I'm skeptical of any such comparisons since they test such different things.

ACT any random person off the street can take it and do okay. That means like if you are smart, you can expect to score reasonably well (even without preparation).

For MCAT, you can take a smart person off the street but they might fail because they never took the prereqs.

And even for those people who have taken the prereqs (AND prepared), it's still hard to compare.

I know that if you told me to take the ACT today, next week, next month, or a year from now, my score would more or less be the same. Same would apply for SAT.

For MCAT, my score would decrease (I finished studying for MCAT in the summer) as I rapidly forget stuff.
But nonetheless, there's something to be said to someone who scores a certain score on one test (ACT) as far as what they could expect, given a standard amount of study time, regarding the MCAT (assuming they took the majority of the prereqs, like 95% of the people who take the MCAT have). I agree that it may not be extremely accurate, but I will say that the average deviation of the sample of 51 people who posted their respective scored from the modified model was less than 3.

And there is, more or less, at least some predictive power.
 
But nonetheless, there's something to be said to someone who scores a certain score on one test (ACT) as far as what they could expect given a standard amount of study time on the MCAT (assuming they took the majority of the prereqs, like 95% of the people who take the MCAT have). I agree that it may not be extremely accurate, but I will say that the average deviation of the sample of 51 people who posted their respective scored from the modified model was less than 3.

Well yes those things would be like innate intelligence and hard work (discipline).

I'm sure my scores will fall in line with your data set but I tried soo much harder on the MCAT than I did on the SAT/ACT.
 
Well yes those things would be like innate intelligence and hard work (discipline).

I'm sure my scores will fall in line with your data set but I tried soo much harder on the MCAT than I did on the SAT/ACT.
But almost EVERYBODY who takes the MCAT tries much harder on it than on the ACT or SAT.
 
There was this excel chart floating around on SDN that generates a predicted MCAT score based on your GPA, ACT, SAT, and other test scores you can provide.

http://forums.studentdoctor.net/thr...et-w-poll-how-accurate-was-it-for-you.753499/

I'm not sure of the correlation...I got a 35 on ACT and 2250 on SAT, and feel like I'm going to fail the MCAT right now. I think this correlation might have to do with how well the undergrad courses prepared the tester. (Purely speculation, of course). Generally, kids with high standardized test scores end up at pretty good colleges and the science courses' rigor probably prepared them well for the MCAT. I chose to go to a pretty crappy undergrad for financial reasons, and am totally regretting it at this point. The highest score a pre-med has gotten at my school was a 28 on his/her MCAT (according to my pre-health advisor).....so, this scares me sh*tless.
 

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There was this excel chart floating around on SDN that generate a predicted MCAT score based on your GPA, ACT, SAT, and other test scores you can provide.

http://forums.studentdoctor.net/thr...et-w-poll-how-accurate-was-it-for-you.753499/

I'm not sure of the correlation...I got a 35 on ACT and 2250 on SAT, and feel like I'm going to fail the MCAT right now. I think this correlation might have to do with how well the undergrad courses prepared the tester. (Purely speculation, of course). Generally, kids with high standardized test scores end up at pretty good colleges and the science courses' rigor probably prepared them well for the MCAT. I chose to go to a pretty crappy undergrad for financial reasons, and am totally regretting it at this point. The highest score a pre-med has gotten at my school was a 28 on his/her MCAT (according to my pre-health advisor).....so, this scares me sh*tless.
I took all of my prereqs at a community college and I did decently. If you can put in the time on your own with your own study materials, hopefully any differences will for the most part even out. I think the biggest separator (out of factors controlled by the will of test-takers) between those who study for and take the MCAT is not what college they went to but rather their long-term reading habits. Assuming the person put the same amount of effort into their education in both situations.

Interesting spreadsheet. I can't comment on its accuracy because I don't know the methods used to create it. It appears statistics were used, which is interesting. There are, of course, obvious flaws if you read the posts by people who used it; it is interesting, though, regardless.
 
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Well yes those things would be like innate intelligence and hard work (discipline).

I'm sure my scores will fall in line with your data set but I tried soo much harder on the MCAT than I did on the SAT/ACT.

^^^

My MCAT was 5-6 points higher than your chart predicts. I didn't get smarter, I just worked harder. To be fair though I think I underperformed on the ACT, so perhaps an SAT->MCAT might be more predictive for me.
 
^^^

My MCAT was 5-6 points higher than your chart predicts. I didn't get smarter, I just worked harder. To be fair though I think I underperformed on the ACT, so perhaps an SAT->MCAT might be more predictive for me.
Perhaps your SAT was more representative. I think just as most people list their latest test score as "their score" on the ACT, the best test to use for this table is your latest. I can't comment if you scored significantly lower on the ACT than the SAT despite taking the former first, though. There is a ACT-SAT conversion table here:
http://www.act.org/solutions/college-career-readiness/compare-act-sat/
 
Wow, spot on in my case. I took the ACT twice, first time got a 28, second time got a 33.

I also took the MCAT twice, first time got a 31, second time got a 38.
 
omg TL;DR haha

I'd posit that the biggest confounding factors in this relationship are the differences in maturity, educational standardization pre-test (HS vs Ugrad coursework), and prep or lack thereof.

n=1, but in my case I got 30, 31, and 33 on the ACT with zero prep or effort, and scored ~10 points higher on the MCAT with max effort prep.

Edit: I will read the entire OP in a minute, don't mean to be rude. 🙂
 
ACT 33
MCAT 41

Good analysis, though I bet things get messy at the high end of both exams since the curves become less forgiving. When missing 1 question = 1 point score drop there's bound to be a big chance factor less present in the middle of the distribution.
 
omg TL;DR haha

I'd posit that the biggest confounding factors in this relationship are the differences in maturity, educational standardization pre-test (HS vs Ugrad coursework), and prep or lack thereof.

n=1, but in my case I got 30, 31, and 33 on the ACT with zero prep or effort, and scored ~10 points higher on the MCAT with max effort prep.

Edit: I will read the entire OP in a minute, don't mean to be rude. 🙂
Lol, I was going to shorten it up, but haven't gotten around to it. The table that I used primarily involved people's latest exam, so at the very least the ACT score that you would use would be your latest and best. Most people reported only one score and it is also true that seemingly most people take these tests (ACT/SAT) more than one time, which is why I say this. Just saying. So then if we take these predictions as truth, you would be predicted to have overperformed by about 5-6 points (if I remember correctly, hehe). Any thoughts on what method is the better?

ACT 33
MCAT 41

Good analysis, though I bet things get messy at the high end of both exams since the curves become less forgiving. When missing 1 question = 1 point score drop there's bound to be a big chance factor less present in the middle of the distribution.
I think you're probably right. Perhaps it also has something to do with the relatively low percentile cap a score of 36 gives in the various subsections. Because at the top composite scores, more people have scores that are restricted in some subsection in which they are particularly gifted, it's possible that the people at the very top of the percentile ranges are more likely to have skewed scores relative to what they are actually capable of. Although this isn't to say that the average person with a 33+ ACT has a "true score" or "true percentile" that is higher than the percentile their composite defines, but rather that that ceiling is a barrier to precise measuring. It wouldn't make sense that, on average, all of the people scoring at the 99%ile would have a true percentile that is slightly higher than the 99%ile (how logical would that be). Therefore the table should be accurate, but not necessarily precise on an individual basis. And yes, I was using the definitions of "precise" and "accurate" in the rigorous sense.

The "harsh curve" idea sounds even more likely/generally correct, I just wanted to point the ceiling thing out.
 
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The only thing I can think in reading through this is "why are you wasting your time on (most likely bogus and) misleading correlations when you could be studying for the MCAT?"
You should go study for the MCAT. Before this nerd-snipes you.

nerd_sniping.png
 
The only thing I can think in reading through this is "why are you wasting your time on (most likely bogus and) misleading correlations when you could be studying for the MCAT?"
You should go study for the MCAT. Before this nerd-snipes you.

nerd_sniping.png
This thread is only for people who have ALREADY taken the MCAT and people who haven't started studying for the MCAT yet. No time-wasting intended 😉. No one else is even allowed.
 
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No time-wasting intended 😉.
Lol...suuure, right. Hey, if you've got nothing better to do, then knock yourself out. Here's a website you might enjoy as well...

This thread is only for people who have ALREADY taken the MCAT and people who haven't started studying for the MCAT yet.... No one else is even allowed.
You know that's not how the internet works, right? 😛
 
I always wondered why the MCAT wasn't dynamic. They clearly have a giant bank of passages and questions, and a lot of data on how "hard" each one is based on % getting it correct on past exams/trial sections.

In theory it would be pretty easy for the MCAT to be an exam of initially easy passages constantly increasing in difficulty until some threshold, say extended period of 60% correctness, at which point the taker is assigned a percentile score on how high their threshold was. A lot less luck is involved this way and it removes the "ceiling" effect since nobody could get all of the hardest questions right even in their strong subjects.
 
I always wondered why the MCAT wasn't dynamic. They clearly have a giant bank of passages and questions, and a lot of data on how "hard" each one is based on % getting it correct on past exams/trial sections.

In theory it would be pretty easy for the MCAT to be an exam of initially easy passages constantly increasing in difficulty until some threshold, say extended period of 60% correctness, at which point the taker is assigned a percentile score on how high their threshold was. A lot less luck is involved this way and it removes the "ceiling" effect since nobody could get all of the hardest questions right even in their strong subjects.
That's significantly different from how the Computer Adaptive Testing on, say, the GRE works though.


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I got a 26 (twice) on the ACT and a 30 on the MCAT. so dam whatever you said
26 -> 30, is actually consistent with the table. After all, you would (as per the corrected table) have been predicted to score a 29, which is pretty close to 30 if you ask me. On average, people from the other threads deviated about +/- 3 from their MCAT score as predicted on this chart, so you, my friend, actually fit BETTER than average.
 
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I'm not familiar with the GRE adaptive testing, but I'm sure its better than what I'm describing. Really any kind of dynamic response in difficulty would be great though, it sucks that the high end gets punished so hard on raw score systems (a single question = a full point gained or lost above 40)
 
I'm not familiar with the GRE adaptive testing, but I'm sure its better than what I'm describing. Really any kind of dynamic response in difficulty would be great though, it sucks that the high end gets punished so hard on raw score systems (a single question = a full point gained or lost above 40)

While I agree with you, from the standpoint of medical school admissions I'm not sure there's any sort of measurable upside to getting a better separation between applicants with really high scores. There aren't that many to begin with and the MCAT will not be keeping them out of schools.
 
I'm not familiar with the GRE adaptive testing, but I'm sure its better than what I'm describing. Really any kind of dynamic response in difficulty would be great though, it sucks that the high end gets punished so hard on raw score systems (a single question = a full point gained or lost above 40)
Trust me, I sympathize with you about the scaling at the high end. At the same time, I'm not comfortable with the CAT as used on the GRE. One disadvantage of that sort of testing is that test takers actually NEED to be informed on the proper strategy in taking the test (time allocation in particular) in order to maintain the psychometric soundness of the test; it needlessly complicates things without much useful gain IMO.


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Wow, spot on in my case. I took the ACT twice, first time got a 28, second time got a 33.

I also took the MCAT twice, first time got a 31, second time got a 38.

n=1, but in my case I got 30, 31, and 33 on the ACT with zero prep or effort, and scored ~10 points higher on the MCAT with max effort prep.

ACT 33
MCAT 41

I got a 26 (twice) on the ACT and a 30 on the MCAT.

33 ACT 38 MCAT

35 ACT
39 MCAT
Thanks guys, for the data. I'm looking forward to seeing similar responses.
 
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I didn't read the whole thing, but I see you compared ACT percentiles to MCAT percentiles. I don't think this makes sense, because the quality of students taking the ACT are not the same as those taking the MCAT. The bottom ~60% (completely made up this number for the sake of discussion) of ACT takers will not take the MCAT. So the people at the top 1% of the ACT might be more like the top 3-5% of the MCAT - if the scores even correlate well.

For what it's worth, I scored a 36 on the ACT and 37 on the MCAT. In my opinion, once you reach the high 30s, there are huge diminishing returns on studying more for the test. There is so much more that you have to know to miss only a few questions, and small amounts of variance on your test day make a bigger difference.
 
I didn't read the whole thing, but I see you compared ACT percentiles to MCAT percentiles. I don't think this makes sense, because the quality of students taking the ACT are not the same as those taking the MCAT. The bottom ~60% (completely made up this number for the sake of discussion) of ACT takers will not take the MCAT. So the people at the top 1% of the ACT might be more like the top 3-5% of the MCAT - if the scores even correlate well.

For what it's worth, I scored a 36 on the ACT and 37 on the MCAT. In my opinion, once you reach the high 30s, there are huge diminishing returns on studying more for the test. There is so much more that you have to know to miss only a few questions, and small amounts of variance on your test day make a bigger difference.
What are you talking about, that I "compared percentiles"? The way you say that, you suggest that I suggested that a 80th percentile on the one would suggest an 80th percentile on the other. If you would have read the method, you would know that I called a 85th percentile on the ACT merely a 72nd percentile on the MCAT, and used that as my standard. You could have gotten this information by reading the post, or even spending 2 seconds to look at the tables included in the OP.

Even your specific example, in which you say that the top 1% of the ACT should correspond to the upper 3-5th percentiles on the MCAT is surprisingly substantiated to a large extent by my post. It is found by looking at the table that a top 1% ACT (33.5) (technically, the score where 1% scored higher than the average person with this score) is estimated to be about top 2% on the MCAT (37.2). So before you claim inconsistencies, I believe that you should verify that the post has inconsistencies, especially those that you specifically cite as probably present. Just saying.

Anyways, thanks for the thoughts. I'm sure you'll be glad to find that I did indeed take such ideas into account and in fact, the idea that the percentiles are not equivalent was the basis for this approach. Good job on your tests, btw.
 
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I did look at the tables, and I guess I am agreeing that there should not be great agreement at the high end. The table shows the top 99.98% of the ACT with the top 99.96% on the mcat. I think it would be more realistic to say that most 35+ on the mcat had a score of 33+ on the act.

We seem to basically be in agreement though.
 
I did look at the tables, and I guess I am agreeing that there should not be great agreement at the high end. The table shows the top 99.98% of the ACT with the top 99.96% on the mcat. I think it would be more realistic to say that most 35+ on the mcat had a score of 33+ on the act.

We seem to basically be in agreement though.
By the way, that is to say that the rarity of 1 in X on the ACT will be (about) twice as common on the MCAT (2 in X). For example, an 90th percentile on the ACT would be approximately equal to 80th on the MCAT and likewise, a 99.98 on the ACT would correspond to 99.96 on the MCAT.

[[Edit: The following is intended to explicitly refer to the rarity of a result only: And so even though 99.98 would look like it is too similar to 99.96, the fact is that it is twice as rare (on the one test) as the other. It's the same difference in rarity as 88th and 94th percentile. Just like you wouldn't say that the 88th and 87th percentiles are different in the same way that 99th and 98th percentiles are different; the former only differ in rarity by a factor of 13/12, but the latter differ by a factor of 2. If you don't think that a factor of 2 is significant, consider: the small group of people that could be considered to be approximately at the border of top third of the people in your average college class, are they not, on average, slightly and possibly even noticeably of a different calibre (on average) than those at approximately the bottom third (notice that this would correspond to a difference of 66th and 33rd percentiles in that population, respectively)? And if you were in a class in which the average person is at the 98.5th percentile about [or around there, I am not sure what number we would have to use to make this work out exactly], this would correspond to 99th and 98th percentile in the ACT population. The specifics in the example may not be correct, but the point remains. This is why the 98th percentile, even though only 1.9 percentile points away from the 99.9th percentile, is obviously not necessarily of the same calibre of students (on average). You could also think about it in this way: what if in an imaginary world, only people within the 97th percentile of our population lived? Or better stated: the average person in that world would be at the 98.5th percentile of ours... Then, in that world, people at the 98th percentile of our current world would be BELOW AVERAGE in theirs! And the people at the 99th percentile of our world would be above average in theirs. The people at the 99.9th percentile of our world would be "merely" like the people with an ACT of 31 in their population! Isn't that weird? The point is, even if the percentile difference looks negligible on a large-scale such as the entire ACT population, the difference between the percentiles is more signiificant if we zoom in, for example, as we convert those scores to percentiles in the MCAT population or even more extremely, in the imaginary world with the average person having an academic achievement equivalent to our 98.5th percentile. The implication of this is that while you are under the impression that a 99.98 and 99.96 are way too consistent between the two test percentiles, the fact is that that is still a significant percentile change (a factor of 2) that is more evident if we look at a more selected for group of people. The difference between percentiles should be considered with respect to relative rarity rather than the magnitude of the difference between the percentiles.

And yes, I agree that is more realistic (and a safer bet) to say that if you do exceptionally well on the ACT, you will be predicted to score within the very high range on the MCAT. But that is a bit too general for the goal of the OP, which was to set up an actual correspondence table to say with a bit more certainty what the rarity of one corresponds to as far as the rarity of the other.

I agree with all of your points; that's the thing about these kinds of things: they don't necessarily have great precision in the specific cases (which is why your criticism is valid) even if they are accurate. But nonetheless, the calculations stand until a stronger attack is seen.
 
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You planning to retake MCAT and get that 40, or just going to heartlessly screw up Rhino's data!?
Hahaha. I considered it. I definitely freaked out during the forst two sections, and I was scoring much higher in practice. But among other reasons, it was already July when I got my score back, so it would have been poor strategy. 🙁

Oh well. One acceptance and it will never matter again. 🙂
 
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