Here’s something you should do when beginning a project, and in the middle of a project, and in the end of the project: Clearly specify your goals, and also specify what’s not in your goal set.

Here’s something from from Witold’s slides on baggr, an R package (built on Stan) that does hierarchical modeling for meta-analysis:

Overall goals:

1. Implement all basic meta-analysis models and tools 2. Focus on accessibility, model criticism and comparison 3. Help people avoid basic mistakes 4. Keep the framework flexible and extend to more models

(Probably) not our goal:

5. Build a package for people who already build their models in Stan

I really like this practice of specifying goals. This is so basic that it seems like we should always be doing it—but so often we don’t! Also I like the bit where he specifies something that’s not in his goals.

Again, this all seems so natural when we see it, but it’s something we don’t usually do. We should.