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Chebyshev's Inequality and the Weak Law of Large Numbers

mean
standard deviation
sample sizes
epsilon
new random samples
Chebyshev's inequality states that if
X
1
,
X
2
,...,
X
n
are independent, identically distributed random variables (an iid sample) with common mean
μ
and common standard deviation
σ
and
-
X
is the average of these random variables, then
P
-
X
-μ>ϵ
2
σ
n
2
ϵ
.
An immediate consequence of this is the weak law of large numbers, which states that
P
-
X
-μ>ϵ0
as
n
. The blue dots in the image are the means of 100 different iid samples. In this Demonstration, these samples are drawn from a normal distribution with mean and standard deviation controlled by the top two sliders, but both of these results hold for any underlying distribution (with finite mean). The two red lines mark the endpoints of the interval (
μ-ϵ
,
μ+ϵ
). The dashed line marks the location of the mean
μ
. The fraction of blue dots outside these lines will usually be smaller than the theoretical upper bound given in Chebyshev's inequalityin many instances this bound is very crude.
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