Please complete before the next class.

Make sure that you’ve completed all previous HW first.

## Catching Up

We spend some time finishing up talking about the basics of computing in R from last class. Remember that Misc. Exercise 3 (from last class) is due soon.

## FPP

Read chs. 1 and 2 of FPP (the textbook; see the syllabus) and do the assigned review exercises here. (Note: You only need to do the review exercises for chs. 1 and 2—not every single chapter. We’ll get to the rest over the course of the semester. And yes, there is a reason I include this note.)

## Causal Inference

Read and review your notes and my slides over causality and causal inference. You can find a video version of the slides here. Answer the following questions:

1. Describe the four ways to obtain a correlation.
2. Describe the other, fifth way you can get a correlation (i.e., by tricking yourself).
3. I write that, under randomization, $$R^{obs}_T - R^{obs}_C \approx R^{hyp}_T - R^{hyp}_C$$.
1. What do each of these four quantities refer to? What do we call the left-hand side? The right-hand side?
2. Notice that the equality is not exact. Instead, it is approximate. What is the only reason it is not exact.
3. Explain why randomization allows us to rule out spuriousness and reverse causation.
4. Describe the design of Gerber and Green’s turnout experiment. Describe the results (i.e., what percent of each group voted?). Discuss whether and how you can rule out any of the four possible ways to obtain a correlation.
4. Was Gerber, Green, and Larimer’s study ethical? Carlisle Rainey