probability foundations · Lesson 1 of 10
What is Probability?
Probability
Probability is a number between 0 and 1 that measures how likely an event is to occur. A probability of 0 means impossible, and 1 means certain.
Classical Probability
P(A) = number of favorable outcomes / total number of equally likely outcomes
Three Approaches
Classical probability assumes equally likely outcomes (e.g., dice). Empirical (relative frequency) probability uses observed data. Subjective probability is based on personal judgment or expertise.
Worked Example
Drawing a heart from a standard deck: P(heart) = 13 hearts / 52 cards = 1/4 = 0.25.