Proof of strong law of large number

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SUMMARY

The discussion centers on the proof of the Strong Law of Large Numbers (SLLN), specifically the necessity of assuming that random variables have a finite fourth moment. This assumption is crucial because it ensures the existence of kurtosis, which is defined as the expectation of [(X - μ)/σ]^4. Without a finite fourth moment, the convergence to a mean cannot be guaranteed, undermining the effectiveness of the SLLN.

PREREQUISITES
  • Understanding of the Strong Law of Large Numbers (SLLN)
  • Knowledge of statistical moments, particularly the fourth moment
  • Familiarity with kurtosis and its implications in probability theory
  • Basic concepts of convergence in probability
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  • Research the implications of finite moments in probability theory
  • Study the concept of kurtosis in depth and its role in statistical distributions
  • Explore the differences between the Strong Law of Large Numbers and the Weak Law of Large Numbers
  • Learn about convergence types in probability, including almost sure convergence
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Statisticians, mathematicians, and students studying probability theory who seek a deeper understanding of the Strong Law of Large Numbers and its assumptions.

Darkzo-n
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Hi, i had recently come across the proof of the strong law of large number.
Inside the proof , it assumed the random variable have a finite fourth moment. may i know y is the assumption necessary and why the 4th? why not 2nd or 3rd or 5th?
 
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Hey Darkzo-n and welcome to the forums.

For this problem, the kurtosis is defined as the expectation of [(X - mu)/sigma]^4.

If the distribution has an infinite mean in either direction, then the kurtosis will not exist. If the mean is zero, then X - mu will also be zero as well so that's not an issue.

The gaurantee of a mean of some sort is what makes the Strong law have its power because things converge to some mean, and without this finite quality, the convergence can not take place and the thing won't work.
 

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