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Updated Mar 30, 2026

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Understanding Basic Probability

Mill xx

@millie1515

Probability is all about predicting the chance of something happening,... Show more

Basic Probability

Union
②Intersection
③ Complement

AUB Eether
AorB or both

AnBin both
A and B

A' not in A

Mutually exclusive An B'

A'n

Basic Probability Concepts

Understanding probability starts with three key operations that work just like a Venn diagram. The union (A∪B) means "either A or B or both" - think of it as everything that's in at least one of the circles.

The intersection (A∩B) is where things get interesting - it's only the stuff that's in both A and B simultaneously. Picture the overlapping bit in the middle of two circles. Meanwhile, the complement (A') is simply everything that's NOT in A.

Here's where it gets practical: when two events are mutually exclusive, they can't happen at the same time. If Pr(A∩B) = 0, then A and B are mutually exclusive - like rolling a 3 and a 5 on the same die.

Quick tip: The basic probability formula Pr(A) = number of favoured outcomes ÷ number of possible outcomes is your best friend for almost every probability question you'll face.

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Updated Mar 30, 2026

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1 page

Understanding Basic Probability

Mill xx

@millie1515

Probability is all about predicting the chance of something happening, and it's actually way simpler than most people think. Whether you're working out the odds of getting your favourite song on shuffle or passing your next test, these basic concepts... Show more

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Basic Probability Concepts

Quick tip: The basic probability formula Pr(A) = number of favoured outcomes ÷ number of possible outcomes is your best friend for almost every probability question you'll face.