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.