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Is this MGMAT accurate?

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Is this MGMAT accurate?

by dalwow » Mon Jul 21, 2008 7:55 am
To first give a little background - the first time I took the GMAT I got a 570. At the time I was being ridiculous, and took it without studying. It has been several months and I have taken time to study every day. I purchased the MGMAT practice exams and have been periodically taking those while also working through OG 11. My scores have improved with every test and on the latest MGMAT I scored a 670 (43Q 38V). I am relieved of course because my scores are improving, however I'm hesitant to get too excited because I'm not sure if this is an accurate indicator of real test performance. Does anyone have any direction for this? I plan to take the 2 free tests given by the GMAT administrators soon, but I was hoping to get any counsel anyone may have in the mean time. Thank you.
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by Stacey Koprince » Mon Jul 21, 2008 10:51 am
The standard deviation on our tests is about 50 points, which means your "true" scoring level is within a 50 point range on either side of the scores that you're getting. The standard deviation on the official test is about 30 points. GMATPrep hasn't published an official standard deviation, but it is either the same as the SD for the official test or a little bit higher (depending upon how closely GMATPrep really does mimic the real thing). I usually think of GMATPrep as a 40 point SD, just to be conservative.

So our tests are not quite as precise as the real thing, and probably not quite as precise as GMATPrep, but they're fairly close. In terms of practice tests, GMATPrep is the most precise one available.

The more important thing to notice is the general upward trajectory - it means you really are improving. Keep up the good work! :)
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by dalwow » Mon Jul 21, 2008 11:12 am
Thank you, that is helpful to know.
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by mayonnai5e » Mon Jul 21, 2008 2:20 pm
Dalwow, it's great to hear that you're scores are improving. If you look at my test scores found in my signature you'll see a mysterious 650 that appeared on an exam surrounded by mid 500 scores. That was an anomaly that I think is similar to your concern, but if you look at my later scores, there was a continual upward curve that resulted in a consistent GMAT score on the real test. If you have been using one baseline test (i.e. MGMAT cats every week or PR cats every week), there's no reason to doubt your score improvements. If you were using several different tests then the scores would be more suspect as you would be comparing apples to oranges (based on scoring algorithms).

Sounds like you are doing a great job - keep up with the hard work and we'll hear from you soon in the I Just Beat the GMAT section.
https://www.beatthegmat.com/my-blog-erro ... t4899.html
550 =\ ...560 =\... 650 =) ...570 =( ...540 =*( ...680 =P ... 670 =T ...=T... 650 =T ...700 =) ..690 =) ...710 =D ...GMAT 720 DING!! ;D

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by Ian Stewart » Mon Jul 21, 2008 4:23 pm
Stacey Koprince wrote:The standard deviation on our tests is about 50 points, which means your "true" scoring level is within a 50 point range on either side of the scores that you're getting.
I asked this in another thread, with no response: the standard deviation of what? How are you measuring test-takers' 'true scoring level'? If you are comparing MGMAT test scores with true test scores, how do you account for the improvement people will make by doing simulated tests before their real test? And what account is made for the standard error of both test scores- the simulation test, and the real test?
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by Stacey Koprince » Mon Jul 21, 2008 4:39 pm
I'll ask our algorithm guy to give me an answer to your question and then I'll post it here. I know he compares peoples' MGMAT practice test scores with the official test scores they report to us after they've finished the course (or tutoring). Beyond that, he'll really have to get into the details of how the calculation is made. :)
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by Ian Stewart » Mon Jul 21, 2008 5:22 pm
Stacey Koprince wrote:I'll ask our algorithm guy to give me an answer to your question and then I'll post it here. I know he compares peoples' MGMAT practice test scores with the official test scores they report to us after they've finished the course (or tutoring). Beyond that, he'll really have to get into the details of how the calculation is made. :)
Thank you, Stacey- I ask out of genuine curiosity. It does seem a difficult thing to measure. If practice materials are genuinely useful, people will improve by using them. This means you would not expect (nor want, as a test prep company) exact correspondence between practice test scores and true test scores, at least if, as I assume is done, the practice tests are completed before the true tests. Indeed, one should only find an exact correspondence if the practice test scores are biased, or if the practice tests are pedagogically useless (which is not something I mean to suggest- it's simply a logical consequence of the analysis). So I wonder how you might account for the pedagogical value of simulation tests in the statistical analysis of your test results.
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by Stacey Koprince » Mon Jul 21, 2008 6:15 pm
Here's Tate's response:

"The 50 pts is actually a standard error, not a standard deviation. It’s an estimate of the tracking error of the LATEST practice test prior to the GMAT, vs. the GMAT itself. That means that about 2/3 of the time, our test will predict the GMAT score within 50 pts. Note that the GMAT itself has an internal std error of about 30 points."

See, I told you he should respond, not me. I've been calling it standard deviation all this time. lol :)
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by Ian Stewart » Tue Jul 22, 2008 4:08 am
Thanks for the response- I was interested to know the methodology behind that calculation.
Stacey Koprince wrote:See, I told you he should respond, not me. I've been calling it standard deviation all this time. lol :)
I understood what you meant :). Standard error is just the (estimated) standard deviation of the error in a measurement, so you weren't really wrong anyway.
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by dalwow » Tue Jul 22, 2008 5:08 am
mayonnai5e wrote:Dalwow, it's great to hear that you're scores are improving. If you look at my test scores found in my signature you'll see a mysterious 650 that appeared on an exam surrounded by mid 500 scores. That was an anomaly that I think is similar to your concern, but if you look at my later scores, there was a continual upward curve that resulted in a consistent GMAT score on the real test. If you have been using one baseline test (i.e. MGMAT cats every week or PR cats every week), there's no reason to doubt your score improvements. If you were using several different tests then the scores would be more suspect as you would be comparing apples to oranges (based on scoring algorithms).

Sounds like you are doing a great job - keep up with the hard work and we'll hear from you soon in the I Just Beat the GMAT section.
Thank you for your response. Your score progression looks exactly how I hope mine is progressing. It's good to see there are people who do improve their scores as much as I would like. I certainly hope to get a 700-720.
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