,
9 tweets,
2 min read
Read on Twitter
1/n
I see a spark of agreement looming from this conversation. It is based on (I hope) everyone's agreeing that "we need a DAG for inference, bc it carries the info we need for id." Another spark is the fact that everyone (I hope) is talking about at least TWO DAGs, one residing
I see a spark of agreement looming from this conversation. It is based on (I hope) everyone's agreeing that "we need a DAG for inference, bc it carries the info we need for id." Another spark is the fact that everyone (I hope) is talking about at least TWO DAGs, one residing
2/n
in the mind and tacitly stores your understanding of the relevant domain,
and one (called Full DAG) is what you eventually explicate when you decide to draw it on paper for full analysis. Call the former "mental DAG" (or m-DAG) and the latter ex-DAG (for explicit).
in the mind and tacitly stores your understanding of the relevant domain,
and one (called Full DAG) is what you eventually explicate when you decide to draw it on paper for full analysis. Call the former "mental DAG" (or m-DAG) and the latter ex-DAG (for explicit).
3/n
Scott also introduced a project-specific DAG, or a premade DAG defined by the id-strategy one wishes to use. Call it t-DAG (for template). Barring two repairable exaggerations, I generally agree with Scott's depiction of "practical economists" and CI-theorists.
Scott also introduced a project-specific DAG, or a premade DAG defined by the id-strategy one wishes to use. Call it t-DAG (for template). Barring two repairable exaggerations, I generally agree with Scott's depiction of "practical economists" and CI-theorists.
4/n
But I need to add another brush stroke to facilitate full agreement: The mental DAG and the Full-DAG are the same, while the t-DAG is a fragment
of the former, selectively extracted to match a specific id-strategy.
With these points of agreement, we see that the Full-DAG is
But I need to add another brush stroke to facilitate full agreement: The mental DAG and the Full-DAG are the same, while the t-DAG is a fragment
of the former, selectively extracted to match a specific id-strategy.
With these points of agreement, we see that the Full-DAG is
5/n
used in two different roles. First, mentioned by Scott, to alert us to new id-strategies (eg front-door) which our ancestors have missed lacking complete id-logic. Second, and perhaps more important, to validate matching between the
postulated template-DAG and our mental DAG
used in two different roles. First, mentioned by Scott, to alert us to new id-strategies (eg front-door) which our ancestors have missed lacking complete id-logic. Second, and perhaps more important, to validate matching between the
postulated template-DAG and our mental DAG
6/n
- the ultimate arbiter of plausibility. For example, if we selected an IV strategy, our t-DAG would be the canonical IV-DAG, and matching involves checking whether the exogeneity and exclusion properties assumed in that canonical t-DAG hold in our mental-DAG, which is waiting
- the ultimate arbiter of plausibility. For example, if we selected an IV strategy, our t-DAG would be the canonical IV-DAG, and matching involves checking whether the exogeneity and exclusion properties assumed in that canonical t-DAG hold in our mental-DAG, which is waiting
7/n
passively to be interrogated. This is what we normally call "judging for plausibility". Why then do we insist that even practicing economists learn to read DAGs before engaging in heavy empirical work? Because the task of matching requires reading your m-DAG. What do we mean
passively to be interrogated. This is what we normally call "judging for plausibility". Why then do we insist that even practicing economists learn to read DAGs before engaging in heavy empirical work? Because the task of matching requires reading your m-DAG. What do we mean
8/n
by READING a DAG? We mean taking an arbitrary 4-variable DAG and checking if properties such as exogeneity, exclusion or conditional exclusion hold in it.
It is a matter of checking the plausibility of one's assumptions,
not of discovering new id-strategies.
by READING a DAG? We mean taking an arbitrary 4-variable DAG and checking if properties such as exogeneity, exclusion or conditional exclusion hold in it.
It is a matter of checking the plausibility of one's assumptions,
not of discovering new id-strategies.
9/9
This is why we get suspicious when leaders of "credibility movements"
tell us that they do not need to read DAGs, since they deal with
"real life" problems." IOW: "We hate to show you how poorly we do when things are explicit, trust us to do better in real-life, #Bookofwhy
This is why we get suspicious when leaders of "credibility movements"
tell us that they do not need to read DAGs, since they deal with
"real life" problems." IOW: "We hate to show you how poorly we do when things are explicit, trust us to do better in real-life, #Bookofwhy
