Pages from a Sociometric Notebook: Reconsidering the Effects of Selective Missingness

The effects of selective missingness on the size of observed correlations between scores derived from peer assessment procedures were examined with a sample of 719 boys and girls drawn from 57 peer groups in seven schools in Montréal, Québec, Canada or Barranquilla, a city on the northern Caribbean coast of Colombia in Latin America. Peer groups (i.e., the boys or girls within in a school classroom) in which participation rates exceeded 90% were randomly assigned to either a "complete" or a "missing" group. In separate procedures, children whose scores placed them above the 20th percentile for their group were excluded from the "missing" groups on measures of passive withdrawal, popularity, and aggression. When the correlations observed with the "complete" groups were compared with the correlations observed with the "missing" groups, few differences were observed. These findings are discussed within the context of the effects of missing data on peer assessment techniques and the factors underlying the association between different peer assessment measures.