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?

▲

wjb3 6 hours ago | parent | next [-]

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.

	▲	torginus 4 hours ago \| parent [-]
		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.

▲

jakobnissen 5 hours ago | parent | prev | next [-]

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.

▲

nabla9 5 hours ago | parent | prev | next [-]

15 points is significant difference.

If someone is 15 points above average, they are in 84th percentile, or in top 16%.

▲

DaveZale 5 hours ago | parent | prev | next [-]

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.

▲

Mistletoe 3 hours ago | parent | prev | next [-]

Well 100 would be your average person and 85 would be a person that has difficulty in school and at work with some tasks.

▲

bena 5 hours ago | parent | prev [-]

15 points is right around one standard deviation.

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 5 hours ago | parent [-]

Isn't the whole point of IQ that it is a single number? Or I suppose potentially two numbers if the quotient was expressed as a fraction.

▲

DSMan195276 4 hours ago | parent | next [-]

It's a single number in that if you take an IQ test one time you get one number, but that doesn't mean you'll get that exact number every single time you take an IQ test. Even ignoring more complex questions about them, your score on an IQ test will vary depending on simple things like how tired you are when you take it, so in practice there's some variance and you do not always get the same number every time you take a test.

▲

tptacek 5 hours ago | parent | prev | next [-]

This is a deeper question than it sounds. The "point" of a modern IQ test is to identify cognitive deficits to target interventions. It's abused widely among non-practitioners as a ranking of intelligence, which it is not.

▲

azan_ 5 hours ago | parent [-]

I think it's widely used in research as a marker of intelligence (and for good reason - correlates really well with cognitive abilities).

	▲	tptacek 5 hours ago \| parent [-]
		I don't think we have to hash this out, because "marker of intelligence" and "ranking of intelligence" are not the same thing. A rank implies a reliable scale, which IQ doesn't provide. (It's also just fine if we disagree about this --- researchers do too!)

▲

bena 4 hours ago | parent | prev [-]

I mean, nothing in the human body can be truly represented by a single number.

Even height and weight change throughout the day. People are typically taller and lighter in the morning than in the evening. Weight especially is variable, it can fluctuate up to 5 to 6 pounds.