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Randomness and Sampling
Wednesday October 1 , 2008
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View Full Document Some definitions
•
Stochastic – means randomness.
•
a random variable is value that varies in
some way
•
deterministic is the opposite of random
•
a random value is a “draw” from a random
distribution (it is one sample of all the
possible values of a random variable)
Random vs. Deterministic
X is deterministic because we know that x =
4.
y is random. We know that y = 3, 4, or 5 but
it is not always the same.
Randomness is not completely random
4
=
x
1
4
±
=
y
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View Full Document Random Distributions
•
We often know something about the
type
of randomness that exists
–
Stock price returns: typically vary based on a
lognormal
distribution
–
Annual average wind speeds also typically
follow a rayleigh
distribution
–
time to failure of mechanical parts usually
follow an exponential
distribution
–
sums of many random variables usually follow
a normal
distribution
A Simple Example:
•
X = U[0,1]
•
Y = U[5,15]
where U[a,b] means uniform distribution with
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This note was uploaded on 02/25/2009 for the course BEE 1510 taught by Professor Staff during the Fall '05 term at Cornell University (Engineering School).
 Fall '05
 STAFF

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