I worked yesterday and today on my AAS 223 plenary talk about engineering and large astrophysics projects. It took me ages to figure out what my take-home points should be. Right now I am at: (1) Homogeneous and uniform samples are impossible, unnecessary, and harmful. (2) Calibration programs reduce your overall measurement accuracy. (3) Propagation of uncertainty is very difficult. (4) There is an open challenge of making precise measurements efficiently while still leaving open "discovery space" for new things.