Complementary Events

Definition

Complementary events are two events that are mutually exclusive and collectively exhaustive, meaning that if one event occurs, the other event cannot occur, and together they account for all possible outcomes of a given experiment or situation.

5 Must Know Facts For Your Next Test

1. The sum of the probabilities of complementary events is always equal to 1.
2. Complementary events can be used to simplify probability calculations by focusing on the probability of one event and then subtracting it from 1 to find the probability of the other event.
3. Complementary events are often represented using Venn diagrams, where the two events are shown as non-overlapping regions within a universal set.
4. The concept of complementary events is fundamental to understanding the two basic rules of probability: the addition rule and the multiplication rule.
5. Identifying and understanding complementary events is crucial for solving probability problems, as it allows for efficient and accurate calculations.

Review Questions

• Explain the relationship between complementary events and the addition rule of probability.
  • The addition rule of probability states that the probability of the union of two mutually exclusive events is equal to the sum of their individual probabilities. Complementary events are a special case of mutually exclusive events, where the occurrence of one event automatically implies the non-occurrence of the other event. Therefore, the probability of one complementary event plus the probability of the other complementary event must always sum to 1, as they account for all possible outcomes.
• Describe how the concept of complementary events can be used to simplify probability calculations.
  • Complementary events can be used to simplify probability calculations by focusing on the probability of one event and then subtracting it from 1 to find the probability of the other event. This is particularly useful when the probability of one event is easier to calculate or is already known. By recognizing the complementary nature of the events, the probability of the other event can be determined without the need for additional calculations, saving time and effort in solving probability problems.
• Analyze the role of complementary events in the context of the two basic rules of probability: the addition rule and the multiplication rule.
  • Complementary events are fundamental to understanding the two basic rules of probability. The addition rule states that the probability of the union of two mutually exclusive events is the sum of their individual probabilities. Complementary events are a special case of mutually exclusive events, where the occurrence of one event automatically implies the non-occurrence of the other event. This relationship is crucial for applying the addition rule correctly. Additionally, the concept of complementary events is also important for the multiplication rule, which states that the probability of the intersection of two independent events is the product of their individual probabilities. Recognizing complementary events can help in identifying the appropriate rule to apply when solving probability problems.

Related terms

Mutually Exclusive Events: Mutually exclusive events are events that cannot occur simultaneously, such that if one event happens, the other event cannot happen.

Collectively Exhaustive Events: Collectively exhaustive events are a set of events that account for all possible outcomes of a given experiment or situation, such that at least one of the events must occur.

Probability: Probability is the measure of the likelihood that an event will occur, expressed as a number between 0 and 1, where 0 indicates an impossible event and 1 indicates a certain event.