Probability of Atleast One of the Events Occuring

This refers to the addition rule.

The additional rule determines the probability of atleast one of the events occuring.

P (A or B) = P (A) + P (B) - P (A and B)

If A and B are mutually exclusive, then P(A and B) = 0, so the rule can be simplified as follows:

P (A or B) = P (A) + P (B) for mutually exclusive events A and B.

Example

An investor is contemplating buying one of the two stocks A or B. The probability P(A) that an investor will buy stock A is 0.30. The probability P(B) that the investor will buy stock B is 0.50. The probability that he may buy both P(A and B) is 0.10.

The probability that the investor will buy atleast one of the two stocks (A, or B, or both) is calculated as follows:

P(A or B) = 0.30 + 0.50 – 0.10 = 0.70

Suppose P(A) and P(B) are mutually exclusive events, that is, the investor will buy only one of the two stocks, then:

P(A or B) = 0.30 + 0.50 = 0.80

Create Your Free Account

Create a free account to access this content and join our community of learners.

You'll get access to:

Access the full tutorial
Join our learning community
Track your progress
Bookmark content for later

Learn

Resources

Probability of Atleast One of the Events Occuring

Create Your Free Account

You'll get access to:

Joint Probability of Two Events

Dependent Vs. Independent Events in Probability

Topics

Course Downloads

Probability Concepts