4) The average number of red blood cells per cubic mm in humans is about 5 million. We'll let = 5,000,000, and = 500,000. Let's also assume that the number of red blood cells follows a normal distribution.

a) Give the values for the number of red blood cells for the middle 75% of people.

(Hint/comment: if, for example, you want values for the middle 50%, you need to figure out many percent go in each tail. Note also that you will need two numbers in your answer.)

b) Give the values for the number of red blood cells for the middle 90% of people.

c) Give the 95th percentile.

d) Are you surprised by the answers to (b) and (c)? Explain. If you're not sure what's going on, draw some pictures of the normal curves.

e) Calculate the 1st percentile.

f) Suppose you come across a person with a red blood cell count of 3,500,000 per cubic mm. Would you

think anything was unusual about this person? Why or why not (make sure you explain this!!).