Mathematics

Mr. Clean

14 December, 11:57

A commuter must pass through five traffic lights on her way to work, and she will have to stop at each one that is red. After years of commuting she has developed the following probability distribution for the number of red lights she stops at each day on her way to work:

0 1 2 3 4 5

.05.25.35.15.15.05

Note that the standard deviation of the above probability distribution is = 1.26

How many red lights should she expect to stop at each day on her way to work?

a. 3

b. 2.5

c. 2

d. 2.25

e. 0.35

Suppose each red light delays the commuter 1.5 minutes. What is the standard deviation of the number of minutes that she is delayed by red lights?

a. 2.38

b. 1.89

c. 1.59

d. 3.57

e. 2.25