📚

All Subjects

 > 

📊 

AP Stats

 > 

🎲

Unit 4

4.3 Introduction to Probability

1 min readjune 11, 2020

Aly Moosa

Kanya Shah


The main concepts you need to grasp from this section are the basics of probability and the complement rule. Make sure you understand these key ideas 🔐!

A probability model is a description of some chance process that is made up of two portions: a list of all possible outcomes and the probability for each outcome. The list of all possible outcomes is called a sample space.

📝Basic Probability Rules 

  1. If all outcomes in a sample space are equally likely, the probability that event A occurs is...

    1. P(A) = number of outcomes in event A/ total number of outcomes in the sample space.

  2. The probability of any event is a number between 0 and 1 (proportion).

  3. All possible outcomes MUST add up to 1

  4. The probability that an event does not occur is 1 minus the probability that it does occur. In other words, this refers to the complement rule which says that P(AC) = 1- P(A) where P(AC) is the complement of event A or the probability that event A doesn’t occur. (*Understand how to solve problems using this rule given a scenario mentioning “at least one.”)

Be sure to know how to interpret the probability you calculate. Remember to use context.

🎥Watch: AP Stats - Probability Rules and Random Variables

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2Fmay-the-probability.jpg?alt=media&token=e3fafba5-ea36-4f92-a89a-a34aec9d3f65

Resources:

Courtesy of Make-a-Meme

Was this guide helpful?

Join us on Discord

Thousands of students are studying with us for the AP Statistics exam.

join now

Browse Study Guides By Unit

✏️
Blogs

✍️
Free Response Questions (FRQs)

🧐
Multiple Choice Questions (MCQs)

👆
Unit 1: Exploring One-Variable Data

✌️
Unit 2: Exploring Two-Variable Data

🔎
Unit 3: Collecting Data

📊
Unit 5: Sampling Distributions

⚖️
Unit 6: Inference for Categorical Data: Proportions

😼
Unit 7: Inference for Qualitative Data: Means

✳️
Unit 8: Inference for Categorical Data: Chi-Square

📈
Unit 9: Inference for Quantitative Data: Slopes

Play this on HyperTyper

Practice your typing skills while reading Introduction to Probability

Start Game