Basic Probability Quiz

1. What is the sum of the probabilities of all outcomes in an exhaustive set?

• A. A. 0
• B. B. 0.5
• C. C. 1
• D. D. It depends on the experiment

2. A spinner is spun 80 times and lands on red 20 times. What is the relative frequency of red?

• A. A. $0.2$
• B. B. $0.25$
• C. C. $0.4$
• D. D. $4$

3. A fair coin is tossed 200 times. What is the expected number of tails?

• A. A. $50$
• B. B. $100$
• C. C. $150$
• D. D. $200$

4. $P(\text{A}) = 0.35$ and event B is mutually exclusive with A, with $P(\text{B}) = 0.25$. If A and B are exhaustive together, what is missing from this statement?

• A. A. Nothing — $P(A)+P(B)=0.6\neq1$, so A and B cannot be exhaustive together unless another outcome exists
• B. B. $P(A)+P(B)$ must always equal 1
• C. C. A and B cannot be mutually exclusive
• D. D. The probabilities must be equal

5. Two fair 4-sided dice (numbered 1–4) are rolled and their scores added. Using a possibility space, how many of the 16 equally likely outcomes give a total of 5?

• A. A. 2
• B. B. 3
• C. C. 4
• D. D. 5