Observational data lends itself to analysis useful for large data sets, data that probably do not exhibit orthogonality and situations where we are interested in prediction rather than interpretation. The Generalized Regression platform is the place to build regression models for both designed experiments and observational data. Some things to keep in mind:

• Penalized regression shows great promise for observational data.
• Effect Heredity probably isn’t necessary.
• Use a holdout set if you have enough data, otherwise the AICc.