Maximum Likelihood Estimator

Definition

A maximum likelihood estimator (MLE) is a statistical method used to estimate the parameters of a probability distribution by maximizing the likelihood function. This approach provides estimates that are most consistent with the observed data, making it a widely used technique in statistical inference and estimation theory.

5 Must Know Facts For Your Next Test

1. Maximum likelihood estimators are derived from maximizing the likelihood function, which quantifies how likely a particular set of parameters would produce the observed data.
2. MLEs have desirable properties, such as consistency and asymptotic normality, meaning they tend to produce reliable estimates as the sample size increases.
3. In cases where MLEs are derived from large samples, they tend to achieve the Cramer-Rao lower bound, indicating they are efficient estimators.
4. The MLE method can be applied to various distributions, including normal, exponential, and binomial distributions, showcasing its versatility.
5. MLEs can sometimes lead to biased estimates in small samples, but they become unbiased as the sample size grows larger.

Review Questions

• How does the maximum likelihood estimator relate to the likelihood function and what role does it play in statistical inference?
  • The maximum likelihood estimator is fundamentally tied to the likelihood function, which represents the probability of observing the data given certain parameter values. By maximizing this function, MLE provides parameter estimates that make the observed data most probable. This process is crucial for statistical inference, allowing researchers to draw conclusions about population parameters based on sample data.
• Discuss how the properties of maximum likelihood estimators contribute to their efficiency and reliability in parameter estimation.
  • Maximum likelihood estimators are known for their efficiency and reliability due to properties such as consistency and asymptotic normality. As sample size increases, MLEs converge to the true parameter values, demonstrating consistency. Moreover, MLEs often achieve the Cramer-Rao lower bound in large samples, indicating they have minimum variance among unbiased estimators, which enhances their overall reliability in statistical analysis.
• Evaluate the implications of using maximum likelihood estimators in small sample scenarios and how it contrasts with their performance in large samples.
  • In small sample scenarios, maximum likelihood estimators may exhibit bias and lack efficiency compared to their performance in large samples where they typically become unbiased and attain optimal variance. This discrepancy raises important considerations for researchers when deciding on estimation methods. In practice, understanding these differences helps guide appropriate usage of MLEs and informs about potential adjustments or alternative methods required for accurate estimation in limited data situations.

Related terms

Likelihood Function: A function that measures the plausibility of a parameter value given the observed data, used in the process of finding the maximum likelihood estimator.

Consistent Estimator: An estimator that converges in probability to the true value of the parameter as the sample size increases, indicating reliability in large samples.

Cramer-Rao Lower Bound: A theoretical lower bound on the variance of an unbiased estimator, which provides insight into the efficiency of estimators, including maximum likelihood estimators.