The entries in the table represent the variables associated with the missingness of each incomplete covariate.
We included in the imputation models a wide range of variables predictive of both missingness in the outcomes and of levels of cardiovascular risk factors in those with observed data, including socioeconomic factors, maternal and family characteristics and earlier measures of the offspring's cardiovascular disease risk factors, in order to make sure that this assumption holds.
Here we use data from a recent Internet based smoking cessation trial in order to investigate which of a set of a priori chosen baseline variables are predictive of missingness, and the evidence for and against the "missing=smoking" assumption.
An aim here is to investigate which, if any, of these variables are good predictors, whilst allowing for the possibility that the primary trial outcome itself may also be predictive of its missingness.
27 The imputation model included all the predictors in the alcohol models plus a number of auxiliary variables that were not of direct theoretical interest but were nonetheless predictive of missingness so as to improve the quality of the imputations and make the missing at random assumption more plausible.
The number of missing items was predictive of missingness for all items, with the OR range being from 1.42 (for BP1) to 2.65 (for PF8).
The attempt to simultaneously estimate the baseline covariate and the outcome effects in this selection modelling framework was, as anticipated, not very successful so in section "Is the primary trial outcome predictive of missingness?
We will explore the plausibility of the missing at random assumption and will include in the imputation models any covariate of interest that is predictive of missingness [ 81].
These included variables found to be predictive of missingness (see supplementary tables 1a and b), indicators of socioeconomic adversity, personal characteristics, and maternal psychopathology as well as strong correlates of the outcome variables, such as similar measures from the domains of mental health and substance use collected earlier in the study.
In section "Which baseline variables are predictive of missingness?
