The relationship between randomization, conditional independence, and unconfoundedness is a foundational definition within causal inference methodology, making this claim common knowledge that requires no citation.
The claim states a fundamental methodological definition in causal inference: that randomization combined with conditional independence of observables yields unconfoundedness (or strong ignorability). This is standard textbook definition and foundational statistical theory rather than an empirical hypothesis subject to scientific debate. Following the instructions for STEP 0, trivially true definitions or foundational disciplinary concepts are classified as COMMON_KNOWLEDGE, requiring no citations.