Outcome | Predictor | |||||

Purpose | Reflect what is most meaningful about the outcome measure | Accurately model the association with the outcome | ||||

How to decide? | A priori | Empirically | ||||

What base for logarithm? | Irrelevant, because results will be back-transformed | Choose to be an interpretable amount, e.g., log base 2 -- effect per 2-fold increase in predictor log base 10 -- effect per 10-fold increase | ||||

Back-transform results? | Yes, to obtain multiplicative effects, percent or fold | Not because of predictor transformation. Back- transformation determined by outcome transformation, regardless of predictor transformation | ||||