Today we'll talk about what is required in order to deduce causality from an experiment (Hint: a lot!). We'll introduce the notion of an association between variables or measurements. Sometimes the association can be quite strong without any causal link: see Spurious Correlations, a hilarious take on the concept. We'll talk about observational studies, randomized controlled trials, and natural experiments. We'll see some examples of natural experiments from Economics. We'll also discuss Judea Pearl's notion of the "ladder of causation". Prior to next class you should read Univariate Data - Tables and Arrays (a Jupyter notebook!). You should also complete reading quiz RQ03. We are assigning homework 00 today. It is due by 2359 on 01 FEB but if you turn it in on Blackboard before 2359 on 30 JAN you will get a bonus point so start working on it now :)