We started today with a nice probability problem. Remember:

- The AP exam often starts probability questions with a straightforward normal question.
- You need the answer in part b for part c. If you can't solve b, just make a (reasonable) answer so you can still do part c.
- Make sure to show lots of work. Label the mean, sd, n, p, etc...

We also discussed blocking. More on blocking later this week. Blocks are groups that are homogeneous *with respect to the response variable* (in this case: productivity). Then from the blocks you sort randomly and evenly to the treatments.

- The blocks reduce the variability.
- The randomization reduces the bias.