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Anecdote time/thought experiment: and forgive me, I'm deliberately vague here. Pretend there's a business somewhere. Pretend they implemented a rule that said

Anecdote time/thought experiment: and forgive me, I'm deliberately vague here. Pretend there's a business somewhere. Pretend they implemented a rule that said people had to enter a number/estimate into a box for a certain peice of information before they could proceed to the next box. Pretend as an analyst you're looking at the values resulting some way down the pipe from that data entry point. Do you think it reasonable to assume the distribution of numbers entered into that box that were invalid would be uniformally random? If the answer is no, what numbers do you think people would enter disproportionately?

aetherson 9y ago
It seems tough to me to suggest that people are putting a default 0 in for older siblings but a default non-zero in for younger siblings. Why wouldn't they be consistent? That said, I still don't believe these data. I don't know where the flaw is, but I none the less think there's a flaw. If it were a much smaller effect, it would be much more believable.
- cabalamat 9y ago
  > If it were a much smaller effect, it would be much more believable. Why do you think that? We know that the SSC readership is in many ways quite distinct from the general population, so why do you find it surprising that it has correlations with birth order? Is it because you find it surprising that anything has correlations with birth order?
  - bildung 9y ago
    The effect would have to be smaller because most effects in psychology and sociology are pretty small. Else they would be obvious (common sense) even without field experiments.
    - carlmr 9y ago
      I agree with the other comments here that it is a rather common sense effect, but it has eluded psychological research until now (which is what makes me question it). I know plenty of people who have a common sense view that birth order is important. So that part isn't missing. I can't even grasp how many times I've heard about the middle child being so different. Or being a typical little brother, etc. For me the question is, if it is so obvious and measurable, why is this the first study that finds this obvious effect.
    - xyzzyz 9y ago
      Most effects are small if you sample general population randomly. However, if you make a survey among basketball players, asking them for their height, you're going to find an extremely large effect. And in fact, birth order effect seem to be common wisdom too.
theptip 9y ago
I like this way of approaching the problem, but I don't think it convincingly contradicts the GP's point; if participants were just entering invalid data to skip the question, then I think they would enter a similar type of number in both "# older siblings" and "# younger siblings", e.g. 0 and 0, or 100000 and 100000, or `rand(10)`. The key observation is that I'd expect the same RNG to be used for each of the four fields. I think you'd see much more `0`s in the fake data as well (it's a Schelling point). But if the fake-data population was disproportionately recorded as only children, that would have reduced the first-child effect, not attenuated it.

aetherson 9y ago

It seems tough to me to suggest that people are putting a default 0 in for older siblings but a default non-zero in for younger siblings. Why wouldn't they be consistent? That said, I still don't believe these data. I don't know where the flaw is, but I none the less think there's a flaw. If it were a much smaller effect, it would be much more believable.

cabalamat 9y ago
> If it were a much smaller effect, it would be much more believable. Why do you think that? We know that the SSC readership is in many ways quite distinct from the general population, so why do you find it surprising that it has correlations with birth order? Is it because you find it surprising that anything has correlations with birth order?
- bildung 9y ago
  The effect would have to be smaller because most effects in psychology and sociology are pretty small. Else they would be obvious (common sense) even without field experiments.
  - carlmr 9y ago
    I agree with the other comments here that it is a rather common sense effect, but it has eluded psychological research until now (which is what makes me question it). I know plenty of people who have a common sense view that birth order is important. So that part isn't missing. I can't even grasp how many times I've heard about the middle child being so different. Or being a typical little brother, etc. For me the question is, if it is so obvious and measurable, why is this the first study that finds this obvious effect.
  - xyzzyz 9y ago
    Most effects are small if you sample general population randomly. However, if you make a survey among basketball players, asking them for their height, you're going to find an extremely large effect. And in fact, birth order effect seem to be common wisdom too.

theptip 9y ago

I like this way of approaching the problem, but I don't think it convincingly contradicts the GP's point; if participants were just entering invalid data to skip the question, then I think they would enter a similar type of number in both "# older siblings" and "# younger siblings", e.g. 0 and 0, or 100000 and 100000, or `rand(10)`. The key observation is that I'd expect the same RNG to be used for each of the four fields. I think you'd see much more `0`s in the fake data as well (it's a Schelling point). But if the fake-data population was disproportionately recorded as only children, that would have reduced the first-child effect, not attenuated it.