Abstract
This study explores the performance of the item response tree (IRTree) approach in modeling missing data, comparing its performance to the expectation-maximization (EM) algorithm and multiple imputation (MI) methods. Both simulation and empirical data were used to evaluate these methods across different missing data mechanisms, test lengths, sample sizes, and missing data proportions. Expected a posteriori was used for ability estimation, and bias and root mean square error (RMSE) were calculated. The findings indicate that IRTree provides more accurate ability estimates with lower RMSE than both EM and MI methods. Its overall performance was particularly strong under missing completely at random and missing not at random, especially with longer tests and lower proportions of missing data. However, IRTree was most effective with moderate levels of omitted responses and medium-ability test takers, though its accuracy decreased in cases of extreme omissions and abilities. The study highlights that IRTree is particularly well suited for low-stakes tests and has strong potential for providing deeper insights into the underlying missing data mechanisms within a data set.