The CBS show NCIS stars Mark Harmon as Special Agent Leroy Jethro Gibbs in which his team investigates military-related criminal cases. The character Abigail Sciuto is frequently seen drinking the high-energy caffeine-laden drink Caf-Pow (she keeps a spare in the lab refrigerator). The mean number of Caf-Pows Abby consumes per show is 3. Suppose a 2013 NCIS episode is selected at random.
a. What is the probability that Abby has no Caf-Pows on the show?
b. What is the probability that she is shown having at most 3 Caf-Pows on the show?
c. Suppose Abby has 6 Caf-Pows. Is there any evidence that the number of Caf-Pows per show has changed? Justify your answer?