Three different roads feed into a particular freeway entrance. Suppose that during a fixed time period, the number of cars coming from each road onto the freeway is a random variable, with expected value and standard deviation as given in the table.

Road 1 Road 2 Road 3 Expected value 800 1000 600 Standard deviation 16 25 18

a. What is the expected total number of cars entering the freeway at this point during the period? [Hint: Let Xi the number from road i.]

b. What is the variance of the total number of entering cars? Have you made any assumptions about the relationship between the numbers of cars on the different roads?

(0, 1)

(x, 1  x)

y

b. If there are 36 students in each lab, but pH determinations are not assumed normal, calculate (approximately)

P(.1  .1).