Question: Stop! Find the mean and standard deviation of the number of red lights the commuter in Exercise should expect to hit on her way to work during a 5-day work week.
Exercise: Red lights. A commuter must pass through five traffic lights on her way to work and will have to stop at each one that is red. She estimates the probability model for the number of red lights she hits, as shown below.
X = # of red 0 1 2 3 4 5
P(X = x) 0.05 0.25 0.35 0.15 0.15 0.05
a) How many red lights should she expect to hit each day?
b) What's the standard deviation?