# 2.8 - Lesson 2 Summary

2.8 - Lesson 2 Summary

## Lesson 2 Summary

Probability is important because it tells us the likelihood of events. Understanding conditional probabilities is also important because p-values, which we'll explore in furture lessons, are conditional probabilities. Now that we understand the probability of events, we can move on to understanding random variables and probability distributions, and thus more deeply into inference

Probability of Events
Set Operations Symbol Definition
Intersection $P(A\cap B)$ Probability of A and B
Union $P(A\cup B)$

Probability of A or B

Note: This includes the possibility of A and B

Complement $P(A')$ The probability of NOT A
Conditional $P(A\mid B)$ The probability of A given B

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