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. Author manuscript; available in PMC: 2023 Jan 3.
Published in final edited form as: Eur J Epidemiol. 2022 Jan 3;37(7):713–722. doi: 10.1007/s10654-021-00826-5

Figure 1. Directed acyclic graph of an instrumental variable.

Figure 1

The instrument (the rs4988235 genotype) must be associated with the exposure (milk consumption), it must be independent of unmeasured confounders, and it must be independent of the outcome (hay fever/asthma/lung function) given the exposure (milk consumption) and the unmeasured confounders.