For baseline variables (NU, education, and mean framewise displacement (mFD)) that statistically significantly differed between the two groups, we conducted a preliminary analysis of the regression of functional connectivity on the baseline variable to determine whether that variable should be included as a covariate in an analysis of covariance (ANCOVA) based on recommendations from a standard statistics textbook [37]. Given that 17/25 OUD subjects were tobacco users while 0/25 HC subjects were tobacco users, we were unable to perform ANCOVA but instead compared the functional connectivity of tobacco using OUD subjects to non-tobacco using OUD subjects.
