Probability

Definition

Probability is the measure of the likelihood that an event will occur, expressed as a number between 0 and 1. It quantifies uncertainty and can be calculated using various formulas depending on the context.

5 Must Know Facts For Your Next Test

1. The probability of an event $A$ is given by $P(A) = \frac{\text{number of favorable outcomes}}{\text{total number of outcomes}}$.
2. The sum of probabilities of all possible outcomes in a sample space is always 1.
3. If two events are mutually exclusive, the probability of either occurring is the sum of their individual probabilities: $P(A \cup B) = P(A) + P(B)$.
4. For independent events, the probability of both occurring is the product of their individual probabilities: $P(A \cap B) = P(A) \times P(B)$.
5. Conditional probability, denoted as $P(A|B)$, represents the probability of event $A$ occurring given that event $B$ has occurred.

Review Questions

• What is the formula to calculate the probability of an event?
• How do you find the probability of either event A or B happening if they are mutually exclusive?
• What does conditional probability represent?

Related terms

Sample Space:

The set of all possible outcomes in a probability experiment.

Mutually Exclusive Events:

Two events that cannot occur at the same time.

Independent Events: Two events where the occurrence of one does not affect the occurrence of the other.