Timeline for Positivity violation in Judea Pearl's Smoking -> Tar -> Lung Cancer front-door adjustment example: P(tar|no smoking) = 0?
Current License: CC BY-SA 4.0
5 events
| when toggle format | what | by | license | comment | |
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| Oct 20, 2022 at 3:08 | comment | added | RobertF | I can see why instrumental variable analysis is more popular than front-door adjustment - it's not easy finding a mediator that meets all the assumptions. | |
| Oct 19, 2022 at 19:12 | vote | accept | RobertF | ||
| Oct 19, 2022 at 18:06 | comment | added | Adrian Keister | Well, the critera for being able to use front-door look like this: $Z$ satisfies the front-door criteria relative to $(X,Y)$ if 1. $Z$ intercepts all directed paths from $X$ to $Y,$ 2. There is no backdoor path from $X$ to $Z,$ and 3. All backdoor paths from $Z$ to $Y$ are blocked by $X.$ Plus positivity, as you've noted. If the other factors are causally associated with the treatment, you're probably still fine. If with the outcome, you are likely in trouble, and would not be able to use frontdoor. I'm not quite up to speed on ANCOVA and matching, so I can't comment on that. | |
| Oct 19, 2022 at 18:00 | comment | added | RobertF | Thanks Adrian. If the mediator is influenced by other factors (e.g., second-hand smoke -> tar), then is front-door adjustment completely invalidated if the external factors are also causally associated with the treatment or outcome variables? Or can we control for factors confounded with the mediator and treatment/outcome by using ANCOVA or matching? I know in instrumental variable analysis, variables confounded with both the IV and treatment can be included in the analysis in order to fix IV assumption violations. | |
| Oct 19, 2022 at 17:24 | history | answered | Adrian Keister | CC BY-SA 4.0 |