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Basic probability. Sample Space (S) : set of all outcomes of an experiment Event (E) : any collection of outcomes Probability of an event E, written as P(E) = The fraction of times the event E occurs out of large number trials. Properties. 1. 0≤P(E)≤1 for any event, E.
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Basic probability Sample Space (S): set of all outcomes of an experiment Event (E): any collection of outcomes Probability of an event E, written as P(E) = The fraction of times the event E occurs out of large number trials
Properties 1. 0≤P(E)≤1 for any event, E. 2. P(E)=1 if E is certain to occur. 3.P(E F)=P(E) + P(F), If both E and F cannot happen at the same time. 4. P(S) = 1, if S is sample space
More properties For any Events E and F, • P(EF) = P(E) + P(F) – P(EF) • P(EC) = 1- P(E) • P(ECFC) = P((EF)C) = 1-P(EF) • P(ECFC) = P((EF)C) = 1-P(EF)
Important notation usage Let S be a sample space. For any events A and B, A or B means AB ( In A or in B or both) A and B means AB ( Common in A and B) A does not occur means AC ( Not in A)
Correct AB=S P(AC)= 1- P(A) P(A) + P(B) = .4 P({}) = 0 or P()=0 Not correct A + B = S AC = 1 – A A + B = .4 {} = 0 or = 0 Correct usage of Notation
Correct Mathematical expressions for the given statements Let S be a sample space. For any events E and F, • Probability that either E or F occurs = P(E F) 2. Probability that Neither E nor F occurs = P(EC FC) 3. Probability that exactly one event occurs = P(ECF)+ P(EFC) = [P(F)-P(EF)]+ [P(E)-P(EF)]