Using the German SOEP database and an instrumental variable methodology to address endogeneity issues, they find that there seem to be significant differences between Turks and Germans in terms of the Big Five personality traits.
Analytical methods for this will utilise instrumental variables methodology involving two stage least squares estimation [ 48].
First, instrumental variables methodology only identifies the effect of an intervention or treatment for those individuals whose assignment to treatment is altered by the instrumental variable.
A more detailed description of the instrumental variable methodology, and in particular the various assumptions of this technique, is provided in the supplementary file.
Second, we estimated an adjusted model and finally, we conducted an adjusted comparison using an instrumental variables methodology to account for unobserved confounding.
Importantly, the assumptions required for an instrumental variables methodology are weaker than those required to support a 'standard' analysis, which requires that infants are randomly assigned to hospitals of birth; otherwise the estimated ORs will be biased.
This instrumental variable methodology has only recently been used in the health sciences literature and we are aware of only one other study making use of this in the stroke specific literature.
Our preferred instrumental variables methodology, in the absence of a randomised assignment of infants to units, enabled us to estimate the causal effects of designation and volume of neonatal care provided at the hospital of birth using observational data.
