Doesn’t this still have selection bias, just of a different form?
For an obvious example, a little old granny who can barely walk is far less likely to (successfully) relocate due to a volcano eruption than a 25y old healthy male.
A missing but essential detail: the government compensated these people and provided them with relocation services. Therefore, even the frail were able to relocate.
That does help reduce the selection bias; I don’t see why that would eliminate it?
I was more focused on chance of death not financials. The chance of said little old granny dying before being settled, either on the way or at the time of the initial event, is likely higher than the chance of the 25y old healthy male.
Oh, it wouldn’t eliminate all selection bias, but it certainly would reduce it. I said “avoid selection bias,” but I changed it to “reduce selection bias” in my original post. Thanks for pointing this out.
It’s tough to extract completely unbiased quasi-experimental data from the world. A frail elder dying from a heart attack during the volcanic eruption certainly contributes to selection bias.
It’s tough to extract completely unbiased quasi-experimental data from the world.
Understatement.
I can’t go into more details here unfortunately, and some of the details are changed for various reasons, but one of the best examples I’ve seen of selection bias was roughly the following:
Chips occasionally failed. When chips failed, they were sent to FA[1] where they were decapped[2] and (destructively) examined[3] to see what went wrong. This is a fairly finicky process[4], and about half the chips that went through FA were destroyed in the FA process without really getting any useful info.
Chips that went through FA had a fairly flat failure profile of various different issues, none of which contributed more than a few percent to the overall failure rate.
Only… it turns out that ~40% of chip failures shared a single common cause. Turns out there was an issue that was causing the dies to crack[5], and said chips FA received then promptly discarded because they thought they had cracked the die during the FA process. (FA did occasionally crack the dies, but at about an order of magnitude lower rate than they had thought.)
Doesn’t this still have selection bias, just of a different form?
For an obvious example, a little old granny who can barely walk is far less likely to (successfully) relocate due to a volcano eruption than a 25y old healthy male.
A missing but essential detail: the government compensated these people and provided them with relocation services. Therefore, even the frail were able to relocate.
That does help reduce the selection bias; I don’t see why that would eliminate it?
I was more focused on chance of death not financials. The chance of said little old granny dying before being settled, either on the way or at the time of the initial event, is likely higher than the chance of the 25y old healthy male.
Oh, it wouldn’t eliminate all selection bias, but it certainly would reduce it. I said “avoid selection bias,” but I changed it to “reduce selection bias” in my original post. Thanks for pointing this out.
It’s tough to extract completely unbiased quasi-experimental data from the world. A frail elder dying from a heart attack during the volcanic eruption certainly contributes to selection bias.
Understatement.
I can’t go into more details here unfortunately, and some of the details are changed for various reasons, but one of the best examples I’ve seen of selection bias was roughly the following:
Chips occasionally failed. When chips failed, they were sent to FA[1] where they were decapped[2] and (destructively) examined[3] to see what went wrong. This is a fairly finicky process[4], and about half the chips that went through FA were destroyed in the FA process without really getting any useful info.
Chips that went through FA had a fairly flat failure profile of various different issues, none of which contributed more than a few percent to the overall failure rate.
Only… it turns out that ~40% of chip failures shared a single common cause. Turns out there was an issue that was causing the dies to crack[5], and said chips FA received then promptly discarded because they thought they had cracked the die during the FA process. (FA did occasionally crack the dies, but at about an order of magnitude lower rate than they had thought.)
failure analysis
Removed, very carefully, from their packaging.
e.g. by lapping and using an electron microscope.
To put it mildly.
Amusingly, a cracked die can actually sometimes kind of limp along due to e.g. capacitive coupling. And then you bump it or the temperature changes...