AP Statistics Flashcards: Introduction to Probability
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 14 cards to help you master important concepts.
What is the complement of an event E?
The complement of an event E consists of all outcomes in the sample space that are not in event E.
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What is the complement of an event E?
The complement of an event E consists of all outcomes in the sample space that are not in event E.
What does a probability of 1 for an event signify?
A probability of 1 means the event is certain and will always occur.
A bag contains 10 marbles (3 red, 7 blue). What is the probability of drawing a red marble?
Assuming each draw is equally likely, there are 3 red outcomes out of 10 total outcomes, so the probability is 3/10.
How is the probability of an event E calculated when all outcomes are equally likely?
The probability of event E is the number of outcomes in E divided by the total number of outcomes in the sample space.
If the probability of a flight being on time is 0.85, what is the probability of it not being on time?
The probability of the flight not being on time is the complement, calculated as 1 - 0.85 = 0.15.
How do you calculate the probability of the complement of an event E?
The probability of the complement of event E is calculated as 1 minus the probability of event E, or 1 - P(E).
A coin is flipped 1000 times and lands on heads 490 times. How does this relate to the long-run relative frequency interpretation of probability?
The relative frequency of 490/1000 (or 0.49) is an estimate of the true probability, which gets closer to the theoretical 0.5 as the number of trials increases.
A meteorologist states there is a 30% chance of snow. How should this probability be interpreted?
This means that for a very large number of days with similar atmospheric conditions, it would snow on about 30% of them.
What is a sample space?
The sample space is the set of all possible non-overlapping outcomes of a chance process.
What is the rule for the range of a probability value?
The probability of any event is a number between 0 and 1, inclusive.
Using the complement rule, find the probability of rolling a fair six-sided die and NOT getting a 2.
The probability of rolling a 2 is 1/6. Therefore, the probability of not rolling a 2 is 1 - 1/6 = 5/6.
A fair six-sided die is rolled. What is the probability of rolling a 5?
Since there is 1 outcome of rolling a 5 and 6 total equally likely outcomes, the probability is 1/6.
What is the long-run relative frequency interpretation of probability?
This interpretation states that the probability of an event is the proportion of times the event would occur in a very long series of repetitions.
What does a probability of 0 for an event signify?
A probability of 0 means the event is impossible and will never occur.