1 Randomization and Luck In class, I vaguely mentioned that you can get "unlucky" when you randomize, and I want to go over that a bit more. So let's think of a really simple experiment: we are interested in understanding the effect of a placebo on height. Thankfully, Rafael Irizarry has provided some teaching datasets including one with heights (in inches). Enter the following code to load the dataset. install . packages ("delaba") library (dslabs) data( heights" ) df - as_tibble (heights) Here is conceptually what we are doing. We are going to randomize the students into treatment and control. We are then going to give the treatment students the placebo, and nothing to the control students. After a year, we measure their heights. 1. First, let's do one randomization. We want to randomize students into zero or one with probability .5, which we can do with the rhinom() command. Type df\\Srandom