Classical probability

P(A)=\dfrac{|A|}{|\Omega|}

Result unit: — (liczba z $\langle 0,1\rangle$)

What it describes

The classical definition — the ratio of the number of favorable outcomes to all (equally likely) outcomes.

P(A)

probability of the event

|A|

number of favorable outcomes

|\Omega|

number of all outcomes

When all outcomes are equally likely, the probability is the ratio of the number of favorable outcomes to all outcomes. Always between 0 and 1.

Dice, coins, draws — models with equally likely outcomes.

A die roll — the probability of rolling an even number.

Substitution

|A|=3

(2,4,6),

|\Omega|=6

Result

P=\dfrac{3}{6}=\tfrac12

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