Questions tagged [confounding]

In statistical models, confounding is said to occur when the apparent dependence of the response on a predictor is partially or wholly due to the dependence of both on a third variable not included in the model, or dependence on a linear combination of other variables included in the model.

Confounding
with a variable included in a model is often called multicollinearity. A synonym is aliasing, used in design of experiments.

In statistical models, confounding is said to occur when the apparent dependence of the response on a predictor is partially or wholly due to the dependence of both on a third variable not included in the model. The causal relation, if any, between predictor and response is thus obscured. Observational studies are especially prone to confounding, the only remedy being to include all potential confounders in the model. Experiments mitigate confounding through randomization; though when randomization is restricted by blocking, some main effects or interactions may be partially or wholly confounded with blocks.

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Testing for confounding

Suppose we want to test whether $Z$ is a confounding variable for the effect of $X$ on $Y$. Is it enough to just check unadjusted and adjusted estimates of the coefficient of $X$ and see if they differ? Also, if the difference between the two is…
markk
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Adjusting vs matching

I have a question regarding adjusting vs matching when the confounding status is largely different between groups. For instance, men are more prone to have Parkinson's disease and vascular diseases; whereas, females are more susceptible to…
Willie
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Age and sex are the most common confounders

I'm trying to understand confounders and I read the statement 'Age and sex are the most common confounders.' Can someone explain why this is? I don't fully understand the concept of a confounder to be honest.
user139790
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What if a confounder is also a covariant?

I have 40-year follow-up data on children who had a birth risk. I would like to see if a certain risk that was present at birth affects intelligence at 40 years (this risk may or may not cause damage to the individual). Social and economical…
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What is the difference between a lurking variable and confounding variable?

What's the difference between a lurking variable and a confounding variable? From what I read, both lurking & confounding variables masks the true relationship between a pair of variable, but it is unclear to me how they differ? I read in a few…
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Current design confounds group effect and treatment effect

In my study, I will investigate if generosity in a dictator game changes as an individual’s wealth level increases or decreases, as compared to a stable wealth level. Additionally, I will examine whether transition direction affects these…
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Should one control for non-confounders?

The standard error of the variable of interest $x$ can be calculated as $$s.e.({\hat\beta_x})=\sqrt{VIF_x\frac{\sigma_\varepsilon^2}{nVar(x)}} $$ As usual, $\sigma_\varepsilon^2=\sum_i\varepsilon_i^2 $ is the variance of the regression error and…
Tom Pape
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Can age be an confounder in a study that investigates the effect of an genetic polymorphism on cardiovascular events?

I have a question about confounding. It is about controlling for confounders in an observational study that investigated the effect of several genetic polymorphisms on the occurrence of cardiovascular events. We had to answer questions about this…
Piet
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Help with real examples of non-confounders

I am looking for some real clinical examples for variables that are NOT confounders: 1) variables only impact treatment, but not outcome. 2) variables only impact outcome, but not treatment So the variables in the two sets are not confounders. Any…
Vincent
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Can a confounder affect the exposure and outcome in different directions?

I'm trying to decide if something is a confounder or not. I know that a confounder must be a risk factor for the outcome and it must also be related to the exposure...what I'm not sure about is whether it has to affect the exposure and the outcome…
MatH
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Which analysis when the range of DV is confounded with IV

I have designed a study and am not sure which statistical analysis can best answer my research question. Just to simplify the problem, I have two IVs. IV1 is continuous, and IV2 is a categorical one with three levels. The DV is a continuous numeric…
May
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Are there any adjusting methods for my confounding variables?

In my current experiment, I designed a 2 x 2 repeated measures factorial design. Suppose that first condition has levels of (a / b), and the second condition has levels of (1 / 2). Thus, my factorial design has four groups (a1, a2, b1, b2). When I…