Why you care: To design and run a good online controlled experiment, you need metrics that meet certain characteristics. They must be measurable in the short term (experiment duration) and computable, as well as sufficiently sensitive and timely to be useful for experimentation. If you use multiple metrics to measure success for an experiment, ideally you may want to combine them into an Overall Evaluation Criterion (OEC), which is believed to causally impact long-term objectives. It often requires multiple iterations to adjust and refine the OEC, but as the quotation above, by Eliyahu Goldratt, highlights, it provides a clear alignment mechanism to the organization.