Finally, random-intercepts-only LMEMs used on within-subjects and/or within-items data from populations where subjects and/or items vary in their sensitivity to experimental manipulations always generalize worse than separate F1 and F2 tests, and in many cases, even worse than F1 alone.
Therefore, we expect that mapping item data from Harm Avoidance with Neuroticism will be less perfect than mapping Neuroticism item data from other personality inventories (e.g. EPQ versus NEO neuroticism).
Thus, the power in GWAS substantially increases if item data from multiple inventories are included, if available.
To tackle the problem that different inventories may not assess the same phenotype, we demonstrate how Item-Response Theory (IRT) test linking can be applied to map item data from different inventories to a common metric.
Within the Genetics of Personality Consortium, we demonstrate for two clinically relevant personality traits, Neuroticism and Extraversion, how Item-Response Theory (IRT) can be applied to map item data from different inventories to the same underlying constructs.
Lastly, and most importantly, the IRT approach enables one to make explicit the extent to which item data from multiple inventories can be combined, both within and across cohorts.
The first objective was to determine the feasibility of the IRT approach in linking Neuroticism and Extraversion item data from different inventories: to what extent do the different inventories measure the same constructs?
To conclude, the IRT results show that the Neuroticism and Extraversion item data from different inventories in different cohorts can be harmonized (for general recommendations and an example R analysis script, see Supplementary Materials Online).
The aim of the current post-hoc analysis was to further investigate the efficacy of oral rivastigmine on cognition in severe AD, using SIB item data from the previously reported clinical trial of oral rivastigmine in moderately severe-to-severe AD [ 9].
