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Viliam_Bur comments on [LINK] Why I'm not on the Rationalist Masterlist - Less Wrong Discussion

21 Post author: Apprentice 06 January 2014 12:16AM

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Comment author: Viliam_Bur 10 January 2014 09:38:59AM *  1 point [-]

If the test is normalized for a population A, then if we give it to a population B, the results don't have to be Gaussian. The normalization occurs only once, when the relationship between the raw scores and the IQ values is defined. Later the existing definition can be reused.

You would get somewhat different shape when you a) calibrate the test for population A and then measure population B, or b) calibrate the test for A+B and then measure population B.

Probably the most correct way to compare two populations would be to skip the normalization step and just compare the histograms of raw scores for both populations. (I am not good enough in math to say how exactly.)

Also, I am not sure how much such comparison would depend on the specific test. Let's imagine that we have one population with average IQ 100 and other population with average IQ 120. If we give them a test consisting of IQ-110-hard questions, the two populations will probably seem more different than if we give them a test consisting of a mix of IQ-80-hard and IQ-140-hard questions.

Comment author: NancyLebovitz 10 January 2014 05:19:45PM 1 point [-]

This backs my general notion that for a lot of measurements (especially of people?), we need graphs, not single numbers.

Comment author: Eugine_Nier 11 January 2014 07:46:14AM *  -1 points [-]

Also, I am not sure how much such comparison would depend on the specific test. Let's imagine that we have one population with average IQ 100 and other population with average IQ 120. If we give them a test consisting of IQ-110-hard questions, the two populations will probably seem more different than if we give them a test consisting of a mix of IQ-80-hard and IQ-140-hard questions.

You can compare by looking at which percentile of population B, the median of population A corresponds to.

Edit: also once you've compared several populations this way, you can try to see if there is a way to normalize the test such that the distributions for all the populations have similar shapes.