Title: Congruence-Based Factor Matching for Exploratory Factor Analysis Authors: Aniko Lovik, Vahid Nassiria, Geert Verbeke, Geert Molenberghs Affiliation: KU Leuven - University of Leuven, I-BioStat, Leuven, Belgium; Hasselt University, I-BioStat, Diepenbeek, Belgium Abstract: Exploratory factor analysis and principal component analysis assume independent observations and, in case of missing data, by default a complete case analysis is performed. Ignoring clustering and/or missing data may result in bias. Previously we proposed a method combining multiple imputation (to deal with incompleteness) and multiple out-putation (to account for clustering) with EFA/PCA that solved both issues in a fast and flexible way at the cost of dealing with the analysis of multiple datasets where the order of the obtained factors/principal components varied and the number of factors had to be fixed before matching (Lovik et al., 2018). Our method, based on the maximisation of modified congruence coefficients to match the different datasets/analyses, also required the analyses to be rotated before matching for optimal results. In this study we extend this method to unknown number of factors at the start of the analysis only assuming a simple factor structure in the Thurstonian sense. References: Lovik A., Nassiri V., Verbeke G., & Molenberghs G. (2018). Combining Factors from Different Factor Analyses Based on Factor Congruence. In: Wiberg M., Culpepper S., Janssen R., Gonzalez J., Molenaar D. (eds) Quantitative Psychology. IMPS 2017. Springer Proceedings in Mathematics & Statistics, vol 233. Springer, Cham.