Conditional probability Quiz

1. A bag has 4 red and 6 blue counters. One red is taken and not replaced. What is the probability the next counter is red?

• A. $\frac25$
• B. $\frac{3}{10}$
• C. $\frac13$
• D. $\frac49$

2. $P(A\text{ and }B)=0.12$ and $P(B)=0.4$. What is $P(A\mid B)$?

• A. $0.3$
• B. $0.048$
• C. $0.52$
• D. $3.33$

3. Of 40 people, 25 own a cat and 10 of these also own a dog. What is $P(\text{dog}\mid\text{cat})$?

• A. $\frac14$
• B. $\frac58$
• C. $\frac35$
• D. $\frac25$

4. Which pair of events is dependent?

• A. Two tosses of a coin
• B. Two sweets taken from a bag without replacement
• C. Two throws of a die
• D. Two spins of a fair spinner

5. What does $P(A\mid B)$ mean?

• A. The probability of $A$ and $B$
• B. The probability of $B$ given $A$
• C. The probability of $A$ given that $B$ has happened
• D. The probability of $A$ or $B$