Basic Concepts in Probability Random experiment:an experiment with uncertain outcome (e.g.,tossing a coin,picking a word from text) Sample space:all possible outcomes,e.g., Tossing 2 fair coins,S=[HH,HT,TH,TT} Event:ECS,E happens iff outcome is in E,e.g., E={HH}(all heads) E={HH,TT}(same face) Impossible event ({})certain event (S) 。Probability of Event:1≥P(E)≥0，s.t. -P(S)=1(outcome always in S) -P(AUB)=P(A)+P(B)if (AB)=(e.g.,A=same face,B=different CCF-ADLat University. 5 June25-27,2010 CCF-ADL at Zhengzhou University, June 25-27, 2010 5 Basic Concepts in Probability • Random experiment: an experiment with uncertain outcome (e.g., tossing a coin, picking a word from text) • Sample space: all possible outcomes, e.g., – Tossing 2 fair coins, S ={HH, HT, TH, TT} • Event: ES, E happens iff outcome is in E, e.g., – E={HH} (all heads) – E={HH,TT} (same face) – Impossible event ({}), certain event (S) • Probability of Event : 1P(E) 0, s.t. – P(S)=1 (outcome always in S) – P(A B)=P(A)+P(B) if (AB)= (e.g., A=same face, B=different face)