A0207
Title: Extending modification indices
Authors: Yushu Li - University of Bergen (Norway)
Johan Lyhagen - Uppsala University (Sweden) [presenting]
Abstract: Thematic theories are incomplete, meaning that they do not give a full description of how to specify a model. Rather, they focus on certain aspects of interest, which means that there are parts of the model that need to be empirically decided. This includes lag-lengths in time series analysis, factor structures, and correlations amongst errors in SEM, or control variables in causal inference (sensitivity analysis). In SEM, there are modification indices, mainly for the purpose of improving the fit of the model, that estimate the increase in the likelihood when relaxing a restriction. Subsequently, one can also derive an estimated parameter change when relaxing a restriction. This is generalized to relaxing more than one parameter, focusing on the estimated parameter change in the parameters of interest, and deriving this in the GLM setting as well as in the traditional SEM. Theoretical results and Monte Carlo simulations are included to investigate the small sample properties, and empirical examples to show the usefulness for empirical researchers.
