## A Real Example of a Dependent Event on a Tree Diagram

It is easier to understand a dependent event with an example.## Picking Marbles

A bag contains**3 yellow marbles**and

**2 blue marbles**. Two marbles will be picked from the bag. One marble will be taken out (without being replaced) and then another.

## 1^{st} Pick

In the **1**, a

^{st}pick**Yellow**marble can be chosen or a

**Blue**The two picks can be drawn on a tree diagram:

- There are
**3**yellow marbles out of**5**. The probability of getting a**Yellow**marble is.^{3}⁄_{5} - There are
**2**blue marbles out of**5**. The probability of getting a**Blue**marble is.^{2}⁄_{5}

## 2^{nd} Pick

The 2^{nd}pick

*depends*on the 1

^{st}pick.

__Imagine a__

**1**^{st}Pick Is Yellow**Yellow**marble was picked. There are now different numbers of yellow and blue marbles than there were in the first pick.

- There are
**2**yellow marbles out of**4**. The probability of getting a**Yellow**marble is.^{2}⁄_{4} - There are
**2**blue marbles out of**4**. The probability of getting a**Blue**marble is.^{2}⁄_{4}

__Imagine a__

**1**^{st}Pick Is Blue**Blue**marble was picked. There are now different numbers of yellow and blue marbles than there were in the first pick.

- There are
**3**yellow marbles out of**4**. The probability of getting a**Yellow**marble is.^{3}⁄_{4} - There is
**1**blue marble out of**4**. The probability of getting a**Blue**marble is.^{1}⁄_{4}

## What Is Probability?

A probability is a measure of how likely (how*probable*) an event is to happen. A probability is expressed as a number between 0 (impossible) and 1 (certain). The formula for finding a probability is shown below:

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