Let the random variable Y = the number of snow days in the Sunnydale school system for one

school year. The probability distribution of Y is given below:

Y

0 1 2 3 4 5 6

P(Y) 0.6 0.2 0.08 ? 0.03 0.02 0.01

The next two questions refer to this random variable.

4. P(Y=3 )

PY= must be

(a) 0.10

(b) 0.08

(c) 0.02

(d) 0.03

(e) 0.06

5. If there are more than two snow days, extra days will be added to the school year in June.

What is the probability that extra days are added?

(a) 0.12

(b) 0.06

(c) 0.08

(d) 0.20

(e) 0.03

It has been estimated that 10% of people in the United States are left-handed. Assume that

figure is accurate. If you select 20 people from this population at random, what is the probability

that at least one is left-handed?

(a) 0.12

(b) 0.27

(c) 0.88

(d) 0.73

(e) 0.39

7. In a recent Gallup poll, 58% of Americans said they agree with the statement, "The benefits

of the space program outweigh the costs." If 10 Americans are chosen at random, what is the

probability that 5 or more agree with this statement?

(a) 0.13

(b) 0.20

(c) 0.22

(d) 0.78

(e) 0.80

Choose an adult woman at random. Let the random variable X = the number of children the

chosen women has had. The next two questions concern these data.

8. The probability that a randomly chosen woman has had 3 or more children is

(a) 0.20

(b) 0.87

(c) 0.13

(d) 0.59

(e) 0.07

9. What is the expected value of the number of children a randomly chosen woman has had?

(a) 0.59

(b) 1.29

(c) 1.0

(d) 2.0

(e) 2.5

10. The probability a person is infected by a certain cold virus is 0.2. In a random sample of 12

people is taken, what is the probability that no more that 5 people will be infected by the cold

virus?

(a) 0.0532

(b) 0.927

(c) 0.9861

(d) 0.9806

(e) 0.0039

11. Which of the following could be quantified as a binomial random variable?

(a) The number of persons in an emergency room

(b) The weights of delivery trucks at a supermarket.

(c) The first time you get a speeding ticket.

(d) The square-foot area of houses being built in Preston Hollow.

(e) The number of free throws a player makes out of 20 shots