Peer behavior was assessed at all three assessments using a nine item questionnaire regarding delinquent, antisocial, or otherwise deviant peer behaviors, asking sibling participants to evaluate statements such as “My friends get into trouble with the police” or “My friends work hard to get good grades in school.” Only a single item on this questionnaire referred directly to peer alcohol use (“My friends drink alcohol or beer.”). Each item was scored on a four point scale for proportion of peers exhibiting the indicated behavior (“None of my friends”, “Just a few of my friends”, “Most of my friends”, or “All of my friends”), and item scores were summed.
