PROBABILITIES

PROBABILITIES

1. Addition Law

   • P(A U B) = P (A) + P(B) - P(A ∩ B)
     • If Mutually Exclusive --> P (A U B) = P(A) + P(B)

2. Multiplication Law

   • Independent P (A ∩ B) = P (A) * P (B).
   • Dependent P (A ∩ B) = P (A) * P (BIA)

3. The Counting Principle

   • Permutation
     • "Order does matter"
       • With repetition
         • Choosing r of something that has n different types
         • "n^r"
       • Without repetition
         • Number of permutations of n items taken r at a time.
         • "nPr" = n! / (n-r)!
   • Combiantion
     • "Order does not matter"
     • nCr = n! / r! (n-r)!

4. Probability Distributions

   • Discrete Random Variable
     • Ex. Time it takes to get home from school, height of a student, etc.
   • Continuous Random Variable
     • X is a discrete random variable, if its range is countable, where range is countably infinite

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