Sample space…    Ω = {ω₁,…,ω_n}
Probability…    0 ≤ P(ω_i) ≤ 1
Event…    E ⊆ Ω

• Basic probability theory
  • P(E) = Σ_ω∈E P(ω)
  • P(Ω) = 1
  • P(not E) = P(Ω\E) = 1 – P(E)
  • P(E₁ and E₂) = P(E₁∩E₂) = P(E₁) · P(E₂)   if E₁,E₂ independent
• Expectation
  • event E has probability p ⇒ average number of trials needed to see E is 1/p
  
  
• Combinatorics
  • number of ways to choose k objects from n objects…
    `((n),(k))= (n·(n-1)·…·(n-k+1)) / (1·2·…·k)`