1. Are the groups of customers who areoffered(a) a $100 phone credit or (b) a $5 pre-paid Visa card probabilistically equivalent? Why or why not?

2. Are the groups of customers whosign upfor (a) the $100 phone credit or (b) the $5 pre-paid Visa card probabilistically equivalent? Why or why not?

3. Are the groups of customers whosign upfor (a) the $100 phone credit or (b) the $5 pre-paid Visa card equally pre-disposed to liking Red? Please answer "yes," "no," or "uncertain." Explain why.

4. Answer Blanka Novak's question: "So let's say that 10 percent of users who signed up for the 100 phone credit ended up signing a contract with us. And let's say that only 2 percent of users who did not get the 100 phone credit signed a new contract with us. Does this mean that the 100 phone credit is causally responsible for an eight-percentage point increase in new customer acquisition for customers who expressed an interest in a new phone via Twitter?" Why or why not?

5. Expanding on Blanka Novak's question, is the "eight-percentage point increase in new customer acquisition" likely to overstate or understate the true causal effect? Why?