evaluate thesensitivity of findings to this rather strong assumption,*° a mul-tiple imputation model was fit, in which the association betweenloss to follow-up and abstinence was varied over a broad rangeof possible values (eAppendix B in Supplement 2).
INTERPRETIVE QUESTION: Missing-not-at-random is a strong assumption. If teens lost to follow-up were equally likely to have quit in both groups, this assumption understates the true effect.