Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

Questions tagged [observational-study]

An observational study involves purely observing the state of the world without manipulating it.

The main reason for distinguishing observational studies from others like experimental studies is the difficulty of drawing causal conclusions from them. However if the study has a longitudinal element causal conclusions may be possible.

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Famous easy to understand examples of a confounding variable invalidating a study

Are there any well-known statistical studies that were originally published and thought to be valid, but later had to be thrown out due to a confounding variable that wasn't taken into account? I'm looking for something easy to understand that…
NathanLite
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How well can multiple regression really "control for" covariates?

We’re all familiar with observational studies that attempt to establish a causal link between a nonrandomized predictor X and an outcome by including every imaginable potential confounder in a multiple regression model. By thus “controlling for” all…
half-pass
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Why is Average Treatment Effect different from Average Treatment effect on the Treated?

In RCTs, randomisation balances unmeasured confounders and, I'm told, ATE and ATT would be the same. In observational studies, this is not possible and Propensity Scores are used in various ways to estimate ATT and/or ATE. The analyses that I've…
bobmcpop
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Whether to use structural equation modelling to analyse observational studies in psychology

I've noticed this issue coming up a lot in statistical consulting settings and i was keen to get your thoughts. Context I often speak to research students that have conducted a study approximately as follows: Observational study Sample size might…
Jeromy Anglim
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Is Propensity Score Matching a "MUST" for Scientific Studies?

Recently, I have been reading about Propensity Score Matching : If I have understood this correctly, Propensity Score Matching is used to construct control/treatment groups in scientific studies, in such a way that individuals in the control group…
stats_noob
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What can we say about models on observational data in the absence of instruments?

I've had in the past a number of questions asked of me relating to published papers in a number of areas where regressions (and related models, such as panel models or GLMs) are used on observational data (i.e. data not produced by controlled…
Glen_b
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Confidence interval for average treatment effect from propensity score weighting?

I am trying to estimate the average treatment effect from observational data using propensity score weighting (specifically IPTW). I think I am calculating the ATE correctly, but I don't know how to calculate the confidence interval of the ATE…
JJM
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Observational vs quasi-experimental design?

I am having some difficulty understanding the difference between and identifying an observational vs quasi-experimental design. From my understanding, an observational study is one in which the researcher does not influence the system and only…
elduderino260
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Why is post treatment bias a bias and not just multicollinearity?

In this presentation by Gary King, he discusses post treatment bias as follows: Post treatment bias occurs: when controlling away for the consequences of treatment when causal ordering among predictors is ambiguous or wrong Example of avoidable…
Heisenberg
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What does "case-control" and "cross-sectional" mean in the context of logistic modeling?

While studying logistic modeling, I read the following statement The fact that only odds ratios, not individual risks, can be estimated from logistic modeling in case-control or cross-sectional studies is not surprising. I do not know what do…
user3125
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Difference between marginal and conditional treatment effect? Relating to regression vs. propensity score methods

Peter Austin has a nice introduction to propensity score methods (citation below), and he states that one of the differences between PS methods and plain regression is that PS methods give you a marginal treatment effect, while regression gives you…
JJM
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ANCOVA in observational studies: what are the assumptions?

Using ANCOVA when groups differ on the covariate is controversial, although Tabachnick and Fidell write that this is a plausible function of ANCOVA in quasi-experimental (or observational) studies. As they state: The second use of ANCOVA commonly…
this.is.not.a.nick
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Recurring problem with retrospective data collection study designs I'm seeing

I've noticed a lot of medical research that I am involved in goes as follows: Collect data on 300-1000 patients, including all sorts of baseline characteristics such as BMI, age, gender and then outcome related statistics, so say our outcome is…
Paze
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How to test for and deal with regression toward the mean?

I am working with a large dataset of behavioral data that I am treating (post-hoc) as a time-series experimental design to look for reliable change in a single dependent variable as a result of a treatment. The data comes from user's interaction…
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Weighting on tables

I have a question about terminology. Suppose I have data categorized by three factors A, B, and C, with cell means $\bar{y}_{ijk}$ and cell frequencies $n_{ijk}$, where $i$, $j$, and $k$ index A, B, and C respectively. And suppose I want to…
Russ Lenth
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