Probability

Basic Probability

100

What is the probability of flipping a head on a fair coin?

1/2

200

If you roll a die, what is the probability of rolling an even number?

3/6 or 1/2

300

What is the probability of selecting a red card from a standard deck?

26/52 or 1/2

400

A jar has 5 red, 3 blue, and 2 green marbles. What is the probability of choosing a blue or green marble?

5/10 or 1/2

500

In the set A=[1,2,3,4,5,6,7,8,9,10], what is the probability of choosing a multiple of 3 or a factor of 9?

4/10 or 2/5

Conditional Probability

100

P(A|B) = P(A and B)/_______?

P(B)

200

P(A|B) = 0.3, and P(B) = 0.6. What is P(A and B)?

0.18

300

P(A|B) = 0.8, P(A and B)=.1. What is P(B)?

0.125 or 12.5%

400

In a school, 50% of students play a sport, and 40% of those who play a sport are in honors classes. What is the probability that a randomly selected student is in an honors class given they play a sport?

0.80 or 80%

500

P(A) = 0.4, P(B) = 0.5, P(A and B) = 0.2. What is P(A|B)?

0.4

Independence

100

What does it mean for two events to be independent?

One event does not affect the probability of the other.

200

Are flipping two coins independent events?

Yes

300

P(A) = 0.5, P(B) = 0.4, P(A and B) = 0.2. Are A and B independent?

Yes, because 0.5 × 0.4 = 0.2

400

If A and B are independent, P(A)=.3 and P(B)=.2. What is P(A and B)?

.06 or 6%

500

If A and B are independent, P(A)=.8 and                 P(A and B)=.3. What is P(B)?

0.375 or 37.5%

Compound Events

100

Define a compound event.

An event made up of two or more simple events.

200

What is P(A or B) if A and B are mutually exclusive?

P(A) + P(B)

300

You roll two dice. What’s the probability of getting a sum of 7?

6/36 or 1/6

400

What is the addition rule for compound events?

P(A or B) = P(A) + P(B) – P(A and B)

500

P(A) = 0.5, P(B) = 0.3, P(A and B) = 0.1. What is P(A or B)?

0.7