# Summary

**Sample space:**The set of all possible outcomes**Sample points: Elements of sample space****Event:**A subset of the sample space**Impossible event:**The empty set**Sure event:**The whole sample space**Complementary event or 'not event':**The set or S - A- Event A or B: The set A B
- Event A and B: The set A B
- Event A and not B: The set A - B
- Mutually exclusive event: A and B are mutually exclusive if A B = Ï†
- Exhaustive and mutually exclusive events: Events E1, E2, ... En are mutually exclusive and exhaustive if E1 E2 .. En = S and Ei Ej =Ï† i â‰ j
- Probability: Number P () associated with sample point such that

The number P () is called probability of the outcome . - Equally likely outcomes: All outcomes with equal probability
- Probability of an event: For a finite sample space with equally likely outcomes Probability of an event where n(A) = number of elements, in the set A, n(S) = number of elements in the set S.
- If A and B are any two events, then
- P(A or B) = P(A) + P(B) - P(A and B)
- Equivalently, P(A B) = P(A) + P(B) - P(A B)
- If A and B are mutually exclusive, then P(A or B) = P(A) + P(B)
- If A is any event, then

P(not A) = 1 - P(A)