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Unit 4

4.3 Introduction to Probability

1 min readโ€ขjune 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 ๐Ÿ”!

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.

๐Ÿ“Basic Probability Rulesย 

  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.ย 

  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 doesnโ€™t occur. (*Understand how to solve problems using this rule given a scenario mentioning โ€œat least one.โ€)

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

๐ŸŽฅWatch: AP Stats - Probability Rules and Random Variables



Courtesy of Make-a-Meme

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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

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