It's true, I am Supreme
Nice, but you clicked on the wrong smiley! These are the 'I am super supreme' ones:
And yes, as eliminator said in other words the percentile rank chart is a compilation of the historical data of all achieved scores from the previous 3 years of administered LSAT's (meaning every test taken that the taker did not cancel, hence received a reported score for). LSAC simply puts all that data together and calculates for each scaled score the percentage of test takers in the 3 year pool that scored below it.
For simple illustration, if there were 1000 people that took the LSAT in the last 3 years that received a reported score (didn't cancel), and in that group only 1 person out of the 1000 scored a 180, the corresponding percentile rank for it would be the 99.9th percentile. It's just basic math they use to calculate the comparative performance rank of each scaled score within the pool of test takers. Take the group size = 1000, add up the # of people that scored below each 120-180 score (999 below 180 in the example numbers), then divide that number by total group size. 999 divided by 1000 = 99.9 percent of test scores in the pool were below 180.
If out of the hypothetical 1000, 500 of the reported scores were below 150, then the percentile rank for a 150 would be the 50th percentile.
Since people are used to grading systems where a forced percentile curve is applied to individual groups of test takers when assigning grades (meaning that no matter how well everyone does on a test that the grades must be distributed so that only a pre-determined percentage of students in the group/class receives an A, B, C, D, etc.), many people incorrectly think that the percentile rank/distribution of achieved LSAT scores is a forced curve and that the score conversion chart for each test is intended and adjusted to insure forced maintenance of the bell curve for each group of test takers per administration.
It is not, which is why the percentile rank of each scaled score fluctuates slightly every time they re-calculate and publish the percentile rank chart. The minor annual fluctuations in the percentile ranking chart are due to the varying preparation and skill levels of the pools of people that took the test in the last 3 years.
The percentile ranks do not necessarily hold true per administration when looked at individually rather than looking at the 3 year pool. The distribution of scores for any particular administration can be significantly different than the combined 3 year stats.
Another way to put it for illustration is that if for a few years unprepared people that wouldn't be able to understand what a contrapositive is for the life of them made up the overwhelming majority of test takers, a 150 could end up being a 90th percentile or higher score.
Theoretically, if most test takers became one of the Supremes like Eliminator and kicked major arse on the test getting near perfect raw point scores for a few years a 170 could end up having a 50.1 percentile rank if only 501 of the 1000 scored below 170. The percentiles that form the statistical bell curve are the natural byproduct of the LSAT performance/ability/skill levels of the population of people that took the test in the last 3 years. In a perfect world if everyone that took a particular LSAT got all or very very close to all the questions correct LSAC would give them all high 170's/180's.
The test development process relies on super crazy psychometric math and pre-testing/measuring the comparative difficulty level of each test item. The development and assembly of test forms process is designed to insure as best as possible that no matter which administration you take, whether it is a harder or easier version of the test, and that no matter how well prepared or not well prepared each group of test takers is, each achieved scaled score represents the same performance/skill /ability level with the particular things the LSAT is designed to measure that Law Schools think are important to doing well in LS.
Since it is a standardized test and LSAC has no control over who decides to take the test nor over how well they prep, LSAT scores must be able to be reliably compared across test forms. That is the essence of a standardized test and means that no matter the relative skill level and performance of each group of test takers, a 170 or whatever score will always represent the same skill/performance/proficiency level with the pre-defined skills being tested, kinda like a measuring tape or a ruler is a standardized tool for measuring length. No matter what/who you measure with it and when, 12 inches always measures as and is reported as 12 inches.
I can go into additional detail if anyone wants to dork out more about LSAT design and psychometrics.
Hopefully the above is enough for me to qualify to be allowed to join the new Supremes band and sing duets with Eliminator!
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