I don't know much about IQ. In the most extreme case, of dissimilar education, the different was about 15 points. Is that a lot? What does that mean to laypeople?
On IQ tests, 15 points is a meaningful difference (one standard deviation), or roughly the gap between solidly average and clearly above average. It doesn’t make anyone a genius or a write-off. Still, we’d expect the higher-scoring person to generally find new learning and problem-solving easier, on average, if everything else is equal.
I'm not even sure it's mathematically appropriate to talk about IQ differences as there's no proof IQ is a linear metric. IQ is defined to have a normal distribution, unlike most things which are measured to have a normal distribution.
With IQ tests, the only thing you know that if 2 people fill it out and one of them scores higher, they have a higher IQ. Based on this you can sort people into a list by increasing IQ, but the standard distribution is implied not discovered.
This is like having a double-sided scale and a bunch of weights - you can similarly compare the weights to each other, and sometimes the arm of the scale will lean to the left, sometimes to the right, by a little or lot - you can postulate that the weights are normally distributed are normally distributed, but they are absolutely not required to be (I can choose them any way I like), so your assumption would be wrong. We know this because we have a direct, not just a comparative measure for weight.
I could make up an imaginary 'weight point' scale based on these comparisons, and say weights A is 5 WP heavier than B and C is also 5 WP heavier than A.
But A might be 100g, B might be 1g, and C might be 1kg.
This is what I think of when I see studies clamining the difference between 2 groups was 5 IQ points.
IQ scores are calibrated to be normally distributed with a standard deviation of 15. So 15 is one standard deviation. That's the difference between average, and being in the smartest 16% of the population. Or being in the smartest 16%, and being in the smartest 2% of the population.
Well a sure component of test scores reflects test taking skills. Years ago, I purchased a book of a series of IQ tests, and my numerical result increased with every test. Another component is confidence. And another is ability. It is said by some that among the first big users of IQ tests was the US Army.
It's not nothing, but IQ is already a little squishy. No one's IQ is a single number. But the article also goes into problems with the study and other potential issues.
Basically, they're saying there is this pattern in the data as recorded, but there are multiple confounding factors and issues with collecting the data in the first place.
wjb3|3 months ago
torginus|3 months ago
With IQ tests, the only thing you know that if 2 people fill it out and one of them scores higher, they have a higher IQ. Based on this you can sort people into a list by increasing IQ, but the standard distribution is implied not discovered.
This is like having a double-sided scale and a bunch of weights - you can similarly compare the weights to each other, and sometimes the arm of the scale will lean to the left, sometimes to the right, by a little or lot - you can postulate that the weights are normally distributed are normally distributed, but they are absolutely not required to be (I can choose them any way I like), so your assumption would be wrong. We know this because we have a direct, not just a comparative measure for weight.
I could make up an imaginary 'weight point' scale based on these comparisons, and say weights A is 5 WP heavier than B and C is also 5 WP heavier than A.
But A might be 100g, B might be 1g, and C might be 1kg.
This is what I think of when I see studies clamining the difference between 2 groups was 5 IQ points.
jakobnissen|3 months ago
DaveZale|3 months ago
bena|3 months ago
It's not nothing, but IQ is already a little squishy. No one's IQ is a single number. But the article also goes into problems with the study and other potential issues.
Basically, they're saying there is this pattern in the data as recorded, but there are multiple confounding factors and issues with collecting the data in the first place.
Aloisius|3 months ago
Mistletoe|3 months ago
nabla9|3 months ago
If someone is 15 points above average, they are in 84th percentile, or in top 16%.