Suppose that a certain bank returns bad checks at a Poisson rate of three per day. What is the probability that this bank returns at most four bad checks during the next two days?

The bus is late or my watch is fast.

In a traditional class with in-class tests, a question that is often asked after a class exam is, "What was the class average?" If that question is asked and the professor says that the class average was 80, what information do the students gain by knowing that? I want you to focus on both what the individual students knows about their own grade as well as what the students know about the class's grades on that exam.

The answers to the question is unclear.