# STAT 200-Masterquiz6 solutions

1. A student is randomly selected from a large college. Define the events C = {the student owns a cell phone} and I = {the student owns an iPod}. Which of the following is the correct interpretation of the probability P(I|C)?
A. The chance that a randomly selected student owns an iPod.
B. The proportion of students who own a cell phone who also own an iPod.
C. The relative frequency of iPod owners who own a cell phone.
D. The percentage of students who own both a cell phone and an iPod.

This is a conditional probability statement (notice the | symbol).
Points Earned: 1/1

2. For the following statement, determine if it is true or false. If two events A and B are mutually exclusive, they must also be independent.
A. True
B. False

False; Just the opposite: if mutually exclusive then independent. Think of the events being Male and being Female. These two events are mutually exclusive since you can only be in one of the events. However, knowing that you are in event Male automatically disqualifies you from being in event Female so the P(male) is dependent on P(female) and vice-versa
Points Earned: 1/1
3. Suppose two different states each pick a two-digit lottery number between 00 and 99 (for a 100 possible numbers). What is the probability that both states pick the number 13?
A. 1/100
B. 1/200
C. 2/100
D. 1/10,000

Probability for each state is 1/100 and these are independent. So getting 13 for each state is (1/100) times (1/100) = 1/10000
Points Earned: 1/1

4. From our Class Survey, 52% of the students reported having tried marijuana, and 24% of students reported that they had tried marijuana and still smoke marijuana. What is the probability that a student still smokes marijuana given that the student has tried marijuana?
A. 0.125
B. 0.76
C. 0.46

This is a conditional probability question, meaning you need to find P(Still gets high | Tried Marijuana) = P(Still and Tried)/P(Tried) = 0.24/0.52 = 0.46 or 46%.
Points Earned: 0/1
5. Which of the following is the sample space when 2 coins are tossed? [H = Head, T = Tail]
A. {H, T, H, T}
B. {HH, HT, TH, TT}
C. {H, T}

The answer is {HH, HT, TH, TT}. When two coins are tossed, for either coin the outcome is a Head or a Tail. Thus there are 22 = 4 possible outcomes.
Points Earned: 1/1

6. Correcly identify if the following random variables as either discrete or continous. The amount of liquid in a gallon of orange juice.
A. Discrete
B. Continuous

Keep in mind that a gallon is a measurement and that if you buy a gallon of OJ you probably do not get exactly one gallon.
Points Earned: 1/1