Use of missing data methods in longitudinal studies: The persistence of bad practices in developmental psychology.

TLDR

Developmental science relies on longitudinal research to describe intraindividual change, yet missing data are common and threaten interpretation. The study examined how often longitudinal reports in three flagship developmental journals report missing data and which techniques they use. The authors sampled 100 longitudinal studies from Child Development, Developmental Psychology, and Journal of Research on Adolescence to assess missing data reporting and methods. Among the 100 studies, 57 reported missing data or inconsistent sample sizes, and 82 % employed problematic techniques such as listwise or pairwise deletion rather than recommended maximum likelihood or multiple imputation.

Abstract

Developmental science rests on describing, explaining, and optimizing intraindividual changes and, hence, empirically requires longitudinal research. Problems of missing data arise in most longitudinal studies, thus creating challenges for interpreting the substance and structure of intraindividual change. Using a sample of reports of longitudinal studies obtained from three flagship developmental journals-Child Development, Developmental Psychology, and Journal of Research on Adolescence-we examined the number of longitudinal studies reporting missing data and the missing data techniques used. Of the 100 longitudinal studies sampled, 57 either reported having missing data or had discrepancies in sample sizes reported for different analyses. The majority of these studies (82%) used missing data techniques that are statistically problematic (either listwise deletion or pairwise deletion) and not among the methods recommended by statisticians (i.e., the direct maximum likelihood method and the multiple imputation method). Implications of these results for developmental theory and application, and the need for understanding the consequences of using statistically inappropriate missing data techniques with actual longitudinal data sets, are discussed.