Probability Formula Review
~.
Types and characteristics
of probability
~
A~ypes
of probability
A
1:, Classical:
peA)
= N
2. Empirical:
peA)
= ~
3.
Subjective: Use empirical formula assuming past
data
of similar events is appropriate.
B.
Probability characteristics
1.
Range for probability:
a
~
PeA)
~ 1
2. Value of complements: P(A) = 1  P(A)
II.
Probability rules
A.
Addition is used to find the sum or union of 2 events.
1.
General
rule:
P(A or B) = P(A) + P(B)

P(A and B)
2.
Special rule:
P(A or B) = P(A) + P(B) is used when events are mutually exclusive.
B.
Multiplication
is used to determine joint probability or the intersection of 2 events.
1.
General rule:
P(A and B) = P(A) x P(B I A)
2.
Special rule:
P(A and B) = P(A) x P(B) is used when the events are independent.
Note: For independent events, the joint probability is the product of the marginal probabilities.
C.
Bayes' theorem is used to find conditional probability.
P(A)
x P(SIA)
P(AIB)
=
P(A) x P(S I A) + p( A J x p( S I A J
Note: The denominator is when condition B
happens. It happens with A and with A.
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 Summer '08
 Staff
 Normal Distribution, Probability, Probability theory, Binomial distribution, iL, Probability Formula Review

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