5 ms·

Surely some studies account for this? If you look for people who do X and people who don't and just analyze their lives, yes this problem is likely to exist. Bu

Surely some studies account for this? If you look for people who do X and people who don't and just analyze their lives, yes this problem is likely to exist. But if you take two randomized samples of a the population and say to group A, "do X," and to group B "don't do X," you have an effective control group. At least I think so. Don't some dietary studies even provide the participants with custom food regimens to try to eliminate extra dietary differences between study participants?

defen 13y ago
You're describing a randomized controlled trial and not an epidemiological study.
- dbecker 13y ago
  You are mistakenly confounding that epidemiological and observational. Epidemiology studies can be randomized or observational.
  - defen 13y ago
    Interesting...what would be an example of a randomized epidemiological study?
spaux 13y ago
What you're describing is the "as long as you omit health-consciousness as a variable" part of his comment.
abraxasz 13y ago
That's one way to do it (the best way). You can still draw "causal" conclusion on observational studies (where you don't get to explicitly assign people to group A and B, but where those assignment are given to you), but it is much harder and you have to be very careful with what you are doing. If you are interested in that topic I suggest you google "Rubin Causal Framework", or check out some of the papers by Donald Rubin (arguably the pioneer of the field of Causal Inference).
EpiMath 13y ago
Epidemiologist here. Many studies account for it and we are acutely aware of this problem and have some sophisticated methods for dealing with unmeasured propensities. And randomized trial are "epidemiologic" studies too. Not everything in epidemiology is observational. Simpson's paradox is taught in 1st year intro to epi courses. There is also a lesser known "reverse-simpson" which comes from overgeneralizing specific results.

defen 13y ago

You're describing a randomized controlled trial and not an epidemiological study.

dbecker 13y ago
You are mistakenly confounding that epidemiological and observational. Epidemiology studies can be randomized or observational.
- defen 13y ago
  Interesting...what would be an example of a randomized epidemiological study?

spaux 13y ago

What you're describing is the "as long as you omit health-consciousness as a variable" part of his comment.

abraxasz 13y ago

That's one way to do it (the best way). You can still draw "causal" conclusion on observational studies (where you don't get to explicitly assign people to group A and B, but where those assignment are given to you), but it is much harder and you have to be very careful with what you are doing. If you are interested in that topic I suggest you google "Rubin Causal Framework", or check out some of the papers by Donald Rubin (arguably the pioneer of the field of Causal Inference).

EpiMath 13y ago

Epidemiologist here. Many studies account for it and we are acutely aware of this problem and have some sophisticated methods for dealing with unmeasured propensities. And randomized trial are "epidemiologic" studies too. Not everything in epidemiology is observational. Simpson's paradox is taught in 1st year intro to epi courses. There is also a lesser known "reverse-simpson" which comes from overgeneralizing specific results.