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I graduated from a public high school and a public university, so I'm going to point out a seeming inconsistency with what you wrote and the web page that was l

I graduated from a public high school and a public university, so I'm going to point out a seeming inconsistency with what you wrote and the web page that was linked to. After checking out the Wikipedia page on Berkson's Paradox, I'm not as sure as I was about my original reasons for disagreeing with you and Graham, but I found a thread I want to pull on. On the Wikipedia page, in discussing a hypothetical situation where the quality of burgers and fries may be positively correlated, but may also be observed to be negatively correlated due to the paradox, it says: "...because they would likely not eat anywhere where both were bad, they fail to allow for the large number of restaurants in this category which would weaken or even flip the correlation" I want to call your attention to the phrase "which would weaken or even flip the correlation". This appears to logically imply that the positive correlation might not be eliminated or flipped, depending on specific circumstances. Therefore your comments such as "[academic performance and private schooling] will be negatively correlated within each student body" (emphasis mine), seem overstated or overconfident. My gut reaction at first was simply that there is an implicit ceteris paribus that's taking too much load here; people aren't assigned to public and private schools at random, and I think that's essentially the same thing as abernard1 was expressing. However, I can't say I completely intuitively understand the paradox, so apart from that, I question whether you are really stating the same principle as is generally accepted. You wrote "you don't need data" and then asked for contrary evidence. If in fact, data is not required, then how can there be contrary evidence?

torstenvl 5y ago
>> because they would likely not eat anywhere where both were bad, they fail to allow for the large number of restaurants in this category which would weaken or even flip the correlation > This appears to logically imply that the positive correlation might not be eliminated or flipped, depending on specific circumstances. No. The negative correlation. The text you quoted is explaining why the negative correlation is observed, even though the underlying population data might show a weaker negative correlation or even a positive correlation. Berkson's paradox is essentially a sampling error. Read it as "anecdotes have sampling bias when competitive market conditions force a trade off in qualities observed anecdotally." The only evidence necessary to show it applies is that there's an economic trade-off: Google hiring people based on experience and coding competitions, singles choosing dates based on personableness and attractiveness, schools admitting students based on educational pedigree and academic performance. > You wrote "you don't need data" and then asked for contrary evidence. That isn't remotely what happened. I believe you may be conflating my discussion of apples with my discussion of schools. I encourage you to try to say only true things about others' positions, please.
- perl4ever 5y ago
  >The text you quoted is explaining why the negative correlation is observed Yes, and it is clearly describing the possibility it shows up, which is inconsistent with it always being the case. I'm trying to condense my point as much as I can. >The only evidence necessary to show it applies is that there's an economic trade-off This looks to me like essentially the same statement as I was referring to - "you don't need data". There is an economic tradeoff, and that's all we need to know. I am not telling you it's a fallacy to reject the possibility of contrary evidence. I'm saying that I doubt the principle is actually that powerful because of the qualified language I've mentioned already. >That isn't remotely what happened From my point of view, you just made the same claim again, so let's avoid the meta-argument and not start rehashing who said what. It only makes misunderstandings worse.
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  - torstenvl 5y ago
    > Yes, and it is clearly describing the possibility it shows up No. It is clearly describing the opposite: the possibility that the underlying situation shows an actually weaker, non-existent, or even inverse correlation. The effect shows up when there's actually a negative correlation. It shows up when there's no correlation. It shows up when the actual correlation is a positive one. So long as there's a trade-off of perceived positive qualities in a competitive market, it always shows up.

torstenvl 5y ago

>> because they would likely not eat anywhere where both were bad, they fail to allow for the large number of restaurants in this category which would weaken or even flip the correlation > This appears to logically imply that the positive correlation might not be eliminated or flipped, depending on specific circumstances. No. The negative correlation. The text you quoted is explaining why the negative correlation is observed, even though the underlying population data might show a weaker negative correlation or even a positive correlation. Berkson's paradox is essentially a sampling error. Read it as "anecdotes have sampling bias when competitive market conditions force a trade off in qualities observed anecdotally." The only evidence necessary to show it applies is that there's an economic trade-off: Google hiring people based on experience and coding competitions, singles choosing dates based on personableness and attractiveness, schools admitting students based on educational pedigree and academic performance. > You wrote "you don't need data" and then asked for contrary evidence. That isn't remotely what happened. I believe you may be conflating my discussion of apples with my discussion of schools. I encourage you to try to say only true things about others' positions, please.

perl4ever 5y ago
>The text you quoted is explaining why the negative correlation is observed Yes, and it is clearly describing the possibility it shows up, which is inconsistent with it always being the case. I'm trying to condense my point as much as I can. >The only evidence necessary to show it applies is that there's an economic trade-off This looks to me like essentially the same statement as I was referring to - "you don't need data". There is an economic tradeoff, and that's all we need to know. I am not telling you it's a fallacy to reject the possibility of contrary evidence. I'm saying that I doubt the principle is actually that powerful because of the qualified language I've mentioned already. >That isn't remotely what happened From my point of view, you just made the same claim again, so let's avoid the meta-argument and not start rehashing who said what. It only makes misunderstandings worse.
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- torstenvl 5y ago
  > Yes, and it is clearly describing the possibility it shows up No. It is clearly describing the opposite: the possibility that the underlying situation shows an actually weaker, non-existent, or even inverse correlation. The effect shows up when there's actually a negative correlation. It shows up when there's no correlation. It shows up when the actual correlation is a positive one. So long as there's a trade-off of perceived positive qualities in a competitive market, it always shows up.