In observational studies, the presence of extraneous variables that distort the apparent relationship between the studied variables is called what?

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Confounding occurs when an extraneous variable is linked to both the exposure and the outcome, creating a distorted or misleading association. In observational studies, you can’t rely on randomization to balance groups, so a confounder can influence both sides of the relationship and make it look like there’s an effect (or hide a real one). To address this, researchers adjust for potential confounders in the analysis or design the study to limit them (through matching or restricting groups). For example, age often relates to both activity levels and cardiovascular risk, so not adjusting for age can bias the observed link between activity and disease. While randomization helps prevent confounding, selection bias and blinding refer to different study design biases. Thus, the distortion described is confounding.