THE EXAMS POINTProbability: events and conditions
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Probability: events and conditions
01 · Sample space S
The set of possible outcomes of the experiment.
02 · Event A
A subset of the sample space.
03 · Equally likely outcomes
P(A) = favourable outcomes ÷ total outcomes, only under this assumption.
04 · Complement
P(not A) = 1 − P(A).
05 · Conditional probability
P(A given B) = P(A ∩ B) ÷ P(B), for P(B) > 0.
06 · Independence
A and B are independent when P(A ∩ B) = P(A)P(B).
Connect the branches
Define the experiment and assumptions before choosing a formula.
Avoid the exam trap
Mutually exclusive events with positive probabilities are not independent.
Test yourself: For a fair die, what is the probability of an even number?
3/6 = 1/2: the favourable outcomes are 2, 4 and 6.
A concise revision aid with simplified connections. It supports the full chapter and primary references; it does not replace them.