# Classical Probability: Definition, Approach & Examples

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Lesson Transcript
Instructor: Karin Gonzalez

Karin has taught middle and high school Health and has a master's degree in social work.

In this lesson, you will learn about classical probability, its formula, and how to convert probability to percentages. You will have a chance to practice your newfound skills with several examples.

## Classical Probability Definition

Probability is a statistical concept that measures the likelihood of something happening. Classical probability is the statistical concept that measures the likelihood of something happening, but in a classic sense, it also means that every statistical experiment will contain elements that are equally likely to happen.

The typical example of classical probability would be a fair dice roll because it is equally probable that you will land on any of the 6 numbers on the die: 1, 2, 3, 4, 5, or 6.

Another example of classical probability would be a coin toss. There is an equal probability that your toss will yield a heads or tails result.

## Determining the Classical Probability

How do we approach determining the classical probability of events occurring? We use a little formula. It's pretty easy to grasp. You can put the number of favorable outcomes (the result we are trying to get) over the total number of possible outcomes and say the probability as a fraction.

We will use this formula in Example 1. Or, you can divide the number of favorable outcomes by the total number of possible outcomes and state the probability as a percentage. We will go over this concept in Examples 2 and 3.

## Example Problems

Let's take a look at a few examples of how to determine probability.

Example 1:

If we wanted to determine the probability of getting an even number when rolling a die, 3 would be the number of favorable outcomes because there are 3 even numbers on a die (and obviously 3 odd numbers). The number of possible outcomes would be 6 because there are 6 numbers on a die. Therefore, the probability of getting an even number when rolling a die is 3/6, or 1/2 when you simplify it.

Example 2:

Take a look at these 7 markers in the colors of red, green, brown, blue, black, yellow, and purple. If you placed them into a Ziploc bag and drew one out while blindfolded, there is an equal chance in probability that you would choose each one, so this is an example of classical probability.

Let's say that we wanted to determine the probability of drawing a red marker out of the bag. There is only 1 red marker, so the number of favorable outcomes is equal to 1. There are a total of 7 markers, so the number of possible outcomes is 7. Therefore, there is a 1/7 chance of getting a red marker!

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