Basic Probability
What is the probability of flipping a head on a fair coin?
1/2
P(A|B) = P(A and B)/_______?
P(B)
What does it mean for two events to be independent?
One event does not affect the probability of the other.
Define a compound event.
An event made up of two or more simple events.
If you roll a die, what is the probability of rolling an even number?
3/6 or 1/2
P(A|B) = 0.3, and P(B) = 0.6. What is P(A and B)?
0.18
Are flipping two coins independent events?
Yes
What is P(A or B) if A and B are mutually exclusive?
P(A) + P(B)
What is the probability of selecting a red card from a standard deck?
26/52 or 1/2
P(A|B) = 0.8, P(A and B)=.1. What is P(B)?
0.125 or 12.5%
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
You roll two dice. What’s the probability of getting a sum of 7?
6/36 or 1/6
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
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%
If A and B are independent, P(A)=.3 and P(B)=.2. What is P(A and B)?
.06 or 6%
What is the addition rule for compound events?
P(A or B) = P(A) + P(B) – P(A and B)
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
P(A) = 0.4, P(B) = 0.5, P(A and B) = 0.2. What is P(A|B)?
0.4
If A and B are independent, P(A)=.8 and P(A and B)=.3. What is P(B)?
0.375 or 37.5%
P(A) = 0.5, P(B) = 0.3, P(A and B) = 0.1. What is P(A or B)?
0.7