Test Prep Advice Post

Are the SAT and ACT "equated" beforehand, "curved" after the test, or both? The answer may surprise you.


Are the SAT and ACT exams truly equated beforehand only?  Is the scoring curve for each test predetermined, as so many seem to think?

The answer is a resounding no--as long as the test is a new test form that has never before been "nationally administered."  Confused?  Keep reading.

That each edition of the SAT or ACT is perfectly equal in difficulty, and that every scoring curve is predetermined with complete accuracy, is certainly what the College Board and ACT Inc. would like us to believe, but historically, there has also been what's called a "smoothing" a.k.a. "curve fitting" process (more popularly known as "curving") after the test is nationally administered for the first time, when a significantly higher amount of student performance information is collected than in the initial equating effort, and the College Board / ACT gains access to a much more sophisticated degree of data about the test.  Thus, additional "fine-tuning" adjustments can be made post-test, and these adjustments are indeed made to the final scoring scale before student scores are released. 

Recent SATs with harsh curves such as the October 24, 2018 PSAT (-1 710 on Math!) and the May 4th, 2019 International SAT serve as further evidence that the College Board doesn't know exactly what the scoring curve will be until after the test is given to to a national sample of students, instead of only a small pretest sample group for equating purposes.

Please note that after the first "national adminstration" (in other words, not a "pretest" or "experimental" version, but the main version) of a test form, the College Board / ACT have historically used the exact same curve for any future administrations of that particular form, regardless of student performance on those future administrations.  This means that if the test form is leaked after the first administration, and some students have an unfair advantage as a result, for example (yes, this has happened with the SAT multiple times), that the cheaters' test results should NOT unfairly affect the curve (aka "ruin the curve") for those who did not cheat. 

As you can see from the below PDFs that you can click to download, this type of intentional pre-test and post-test manipulation of SAT scores (whether it is called recentering, redistributing, equating, smoothing, scaling or curving) has been going on for decades, and most likely continues today, when the vast processing power of computers means that there is no longer a limit on the amount of test-day data that can be processed in order to establish a fair scoring curve for each exam.  Another term for a "fair scoring curve" is "equipercentile equating."

https://www.ets.org/Media/Research/pdf/RR-02-04-Dorans.pdf
https://www.ets.org/Media/Research/pdf/RR-10-29.pdf
https://www.ets.org/Media/Research/pdf/LIVINGSTON2ed.pdf (**read page 20 about "smoothing)," which is another word for curving).  The word "scaling" is also used to describe this process. 

An excerpt: 
"If you want to do equipercentile equating, and you don’t have a good way to smooth the score distributions, there is an alternative. You can perform an equipercentile equating based on the observed distributions, and then smooth the equating relationship. (Some equating experts refer to this approach as “post-smoothing.")"


Source:  Wikipedia

I would also encourage you to read the Wikipedia definition of equating, which states clearly that equating is a pre-test process for raw scores, and that scaling/curving is a post-test process for scaled scores:

"Unlike with item response theory, equating based on classical test theory is somewhat distinct from scaling. Equating is a raw-to-raw transformation in that it estimates a raw score on Form B that is equivalent to each raw score on the base Form A. Any scaling transformation used is then applied on top of, or with, the equating."  

To summarize: SAT and ACT exams are Equated Pre-Test (the content is controlled, compared to previous tests, and standardized to create a test of roughly average difficulty), and Curved/Smoothed/Scaled Post-Test (raw to scaled score conversion tables adjusted) afterwards based upon a more detailed sample of student results on that particular test:  if it turns out that the test was harder than expected, then the curve might bump your score up by a few points, and vice-versa, so that the results of the test more strongly resemble a "smooth" bell-shaped curve.

Can I prove definitively that the ACT and College Board engage in curve-fitting/post-smoothing?  No, because ACT and the College Board haven't explicitly admitted to it yet.   However, we have strong historical evidence (see above), as well as evidence from both the SAT and ACT literature (sources: SAT Technical Manual) / ACT Technical Manual) that curving has been an unstated/largely ignored yet essential part of the "equating" umbrella all along, and that this post-test process is an entirely separate process from any pre-test calculations.

If you read the SAT technical manual, for example, then you will see the term "operational administration," which refers to a national SAT test date when scaling data is collected from a sample group, vs. a "pretest," when equating data is collected prior to the national administration of the test.  The ACT also freely admits to using post-test data from national test dates in its technical manual.  Finally, it is also important to consider that "curved" tests have a bad reputation, so the College Board and ACT have reason to mislead us in this regard.

-Brian

 

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