# Central limit theorem

## Central Limit Theorem[edit | edit source]

The Central Limit Theorem (CLT) is a fundamental concept in probability theory and statistics. It states that, under certain conditions, the sum or average of a large number of independent and identically distributed random variables will follow a normal distribution, regardless of the shape of the original distribution. This theorem has wide-ranging applications in various fields, including finance, physics, and biology.

### Statement[edit | edit source]

The Central Limit Theorem can be stated as follows: Let X₁, X₂, ..., Xₙ be a sequence of independent and identically distributed random variables with a common mean (μ) and standard deviation (σ). Then, as n approaches infinity, the distribution of the sample mean (X̄) approaches a normal distribution with mean μ and standard deviation σ/√n.

### Importance[edit | edit source]

The Central Limit Theorem is of great importance in statistics because it allows us to make inferences about a population based on a sample. It provides a theoretical foundation for many statistical techniques, such as hypothesis testing and confidence intervals. Additionally, it enables us to approximate the distribution of a sum or average of random variables, even if the original distribution is not known.

### Applications[edit | edit source]

The Central Limit Theorem has numerous applications in various fields. In finance, it is used to model stock returns and estimate the risk associated with investment portfolios. In physics, it is employed to analyze experimental data and determine the uncertainty in measurements. In biology, it helps in understanding the variability in biological processes and making predictions based on sample data.

### Proof[edit | edit source]

The proof of the Central Limit Theorem involves concepts from probability theory and mathematical analysis. It typically relies on moment generating functions, characteristic functions, or characteristic equations. The proof can be quite complex and requires a solid understanding of advanced mathematical concepts.

### Limitations[edit | edit source]

While the Central Limit Theorem is a powerful tool, it does have some limitations. It assumes that the random variables are independent and identically distributed, which may not always hold in real-world scenarios. Additionally, the convergence to a normal distribution may be slow for certain distributions with heavy tails. In such cases, alternative methods, such as the use of bootstrap or Monte Carlo simulations, may be more appropriate.

### See Also[edit | edit source]

### References[edit | edit source]

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Contributors: Prab R. Tumpati, MD