When translating equations into path analysis models and vice versa - how do you know when translate and use “+” and " * " - so for example where the is mean = SNP*b1 + b0 in slide 13 of the lectures slides given before the session.
I am unsure what the basic purpose of Path Analysis is; is it something you construct out of intended phenotype/predictor/covariates to dictate the construction of the regression model- or is it dictated by computed components…? Is it contructed before or with the knowledge of additive/dominant genetic variance?
A path diagram is a schematic depiction of a mathematical equation. Most people have an easier time interpreting pictorial depictions than mathematical depictions, but, if the path diagram is sufficiently complete, the algebraic and schematic depictions are equivalent.
Yes, the crucial thing is that a properly drawn path diagram is a mathematically complete description of the model. This identity enables diagrams to be used directly as a model specification which can then be fit together. Onyx-sem.com does this, and there is a diagram interface for OpenMx under development that will add that functionality.