# Expansion Rule for Probabilities

## What Is the Addition Rule for Probabilities?

The expansion rule for probabilities depicts two formulas, one for the likelihood for both of two mutually exclusive occasions occurring and the other for the likelihood of two non-mutually exclusive occasions occurring.

The principal formula is just the sum of the probabilities of the two occasions. The subsequent formula is the sum of the probabilities of the two occasions minus the likelihood that both will happen.

## The Formulas for the Addition Rules for Probabilities Is

Numerically, the likelihood of two mutually exclusive occasions is meant by:

$P(Y \text Z) = P(Y)+P(Z)$

Numerically, the likelihood of two non-mutually exclusive occasions is meant by:

$P(Y \text Z) = P(Y) + P(Z) - P(Y \text Z)$

## What Does the Addition Rule for Probabilities Tell You?

To represent the primary rule in the expansion rule for probabilities, think about a bite the dust with six sides and the chances of rolling either a 3 or a 6. Since the chances of rolling a 3 are 1 of every 6 and the chances of rolling a 6 are likewise 1 out of 6, the chance of rolling either a 3 or a 6 is:

1/6 + 1/6 = 2/6 = 1/3

To outline the subsequent rule, consider a class wherein there are 9 young men and 11 young ladies. Toward the finish of the term, 5 young ladies and 4 young men receive a grade of B. Assuming that a student is chosen by chance, how likely is it that the student will be either a young lady or a B student? Since the chances of choosing a young lady are 11 out of 20, the chances of choosing a B student are 9 out of 20 and the chances of choosing a young lady who is a B student are 5/20, the chances of picking a young lady or a B student are:

11/20 + 9/20 - 5/20 =15/20 = 3/4

In reality, the two rules rearrange to just one rule, the subsequent one. That is on the grounds that in the principal case, the likelihood of two mutually exclusive occasions both happening is 0. In the model with the pass on, moving both a 3 and a 6 on one roll of a single die is unimaginable. So the two occasions are mutually exclusive.

## Mutual Exclusivity

Mutually exclusive is a statistical term portraying at least two occasions that can't concur. It is ordinarily used to portray a situation where the occurrence of one outcome supplants the other. For a fundamental model, think about the rolling of dice. You can't roll both a five and a three at the same time on a single bite the dust. Besides, getting a three on an initial roll no affects whether a subsequent roll yields a five. All rolls of a pass on are independent occasions.

## Features

- In theory the main form of the rule is a special case of the subsequent form.
- Non-mutually-exclusive means that some overlap exists between the two occasions being referred to and the formula makes up for this by deducting the likelihood of the overlap, P(Y and Z), from the sum of the probabilities of Y and Z.
- The expansion rule for probabilities comprises of two rules or formulas, with one that obliges two mutually-exclusive occasions and another that obliges two non-mutually exclusive occasions.