Complement of an Event

Definition of Complement of an Event

• The complement of an event is all the other possible outcomes of the respective experiment.
• If A is an event of an experiment, then its complement is denoted by .

Examples of Complement of an Event

• Suppose a fair six-sided die is rolled.

Let A be the event of rolling a 3, then the complement of

A = = {1, 2, 4, 5, 6}.

 

Solved Example on Complement of an Event

John has 10 cards numbered 1-10, out of which he chose one card randomly. Find the probability of John not choosing a card numbered 7.

Choices:

A.

B.

C.

D.

Correct Answer: D

Solution:

Step 1: The probability of John choosing the card numbered 7 is .

Step 2: The probability of the complement of this event is .

Related Terms for Complement of an Event

• Event
• Outcome
• Experiment

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