Probability Map

Addition Rule "OR"

Mutually Exclusive

r

P(A or B)= P(A) + P(B)

Non Mutually Exclusive

r

P(A or B)= P(A) + P(B)- P(A and B)

Multiplication Rule "AND"

Independent

r

P(A and B)= P(A) * P(B)

Dependent

r

P(A and B)= P(A) * P(B) - P(B/A)

Relative Frequency Approximation of Probability

P(A)= Number of times A occurred/ number of times the procedure was repeated

Probability of Atleast One

P(atleast 1__)= 1-P(o___)

Complementary Events Rule

P(A) +P(À)= 1, P(A)= 1-P(À), P(À)= 1-P(A)

Conditional Probability

P(B/A)= P(A and B)/P(A)

Classical Approach to Probability

s/n

r

P(A)= number of ways A occurs/ number of different simple events

Counting

Fundamental Rule

r

P(E)= number of outcomes with E/ total number of outcomes

Factoral Rule

r

n!= 1*2*...n

Permutations When Items are Different

r

nPr

Permutations When Items are Identical

r

n! / n1! * n2! * nk!

Combinations Rule

r

nCr