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### Course: Praxis Core Math > Unit 1

Lesson 3: Statistics and probability- Data representations | Lesson
- Data representations | Worked example
- Center and spread | Lesson
- Center and spread | Worked example
- Random sampling | Lesson
- Random sampling | Worked example
- Scatterplots | Lesson
- Scatterplots | Worked example
- Interpreting linear models | Lesson
- Interpreting linear models | Worked example
- Correlation and Causation | Lesson
- Correlation and causation | Worked example
- Probability | Lesson
- Probability | Worked example

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# Probability | Lesson

## What is a probability?

A probability indicates the chance that an will happen.

A probability can be any number from $0$ to $1$ .

- A probability of
or$0$ means that an event will$0\mathrm{\%}$ *never*happen. - A probability of
or$\frac{1}{2}$ means that an event is$50\mathrm{\%}$ *equally likely*to happen or not happen. - A probability of
or$1$ means that an event will$100\mathrm{\%}$ *certainly*happen.

The probability that event $A$ will happen is written as $P(A)$ .

The probability that event $A$ will $P(\text{not}A)$ , is equal to $1-P(A)$ .

*not*happen,### What skills are tested?

- Calculating the probability that an event will happen (or will not happen) based on a description of the situation
- Calculating the probability that an event will happen (or will not happen) based on information in a data display
- Calculating a count or quantity from a probability
- Comparing probabilities or drawing conclusions based on probabilities

## How is the probability of an event calculated?

An event could be the outcome of any random process such as the toss of a fair coin, the roll of a fair number cube, or the random selection of an item from a group.

We use the notation $P\left(A\right)$ to represent "the probability that event $A$ will happen".

## How is the probability of an event calculated using information in a data display?

When calculating the probability that a randomly selected item will have certain attribute(s), the information we need may be in a data display.

In such cases,

- The
*ways*is the number of items of type can happen$A$ .$A$ - The number of
*possible outcomes*is the total number in the group.

## How can we calculate a count or quantity from a probability?

Sometimes we are given the probability and are asked to calculate either the number of possible outcomes or the number of ways $A$ can happen

To solve these questions:

- Substitute known values into the equation
.$P(A)={\displaystyle \frac{\text{ways}A\text{can happen}}{\text{possible outcomes}}}$ - Solve for the unknown quantity.

## Your turn!

## Things to remember

A probability indicates the chance that an event will happen.

A probability can be any number between $0$ and $1$ .

The probability that event A will happen is:

The probability that event A will not happen is:

## Want to join the conversation?

- how do you figure out the probability of coins(1 vote)
- You take one side of the coin and see how many total sides there are. one side=1 both sides=2 so, 1/2. Or 50% odds of it landing on one of the sides.(2 votes)