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, which measures how well the chosen model explains the observed data. The MLE connects closely with various important statistical properties, including unbiasedness, consistency, sufficiency, and efficiency, making it a fundamental concept in statistical inference.

5 Must Know Facts For Your Next Test

1. The maximum likelihood estimator is consistent, meaning that as the sample size increases, it converges in probability to the true parameter value.
2. MLEs are asymptotically normal, which means for large samples, their distribution approaches a normal distribution centered around the true parameter value.
3. In general, MLEs can achieve efficiency, meaning they can reach the Cramér-Rao lower bound when certain regularity conditions are met.
4. The process of finding MLE involves taking the derivative of the likelihood function and solving for parameters where this derivative equals zero.
5. MLEs can sometimes be biased in small samples but become unbiased as the sample size increases.

Review Questions

• How do maximum likelihood estimators exhibit unbiasedness and consistency in relation to sample size?
  • Maximum likelihood estimators are designed to provide estimates that converge to the true parameter value as the sample size increases. While MLEs may be biased in small samples, they achieve consistency in larger samples, meaning their estimates will increasingly reflect the true parameters. This behavior allows statisticians to rely on MLEs for accurate parameter estimation when sufficient data is available.
• Discuss how sufficient statistics relate to maximum likelihood estimators and their impact on estimating parameters.
  • Sufficient statistics play a crucial role in maximum likelihood estimation by summarizing all necessary information from the sample needed for estimating parameters. When using sufficient statistics, MLEs can be computed more efficiently because they incorporate all relevant data without redundancy. This relationship enhances the effectiveness of MLEs in capturing parameter information and leads to more reliable estimates.
• Evaluate the significance of the Cramér-Rao lower bound in determining the efficiency of maximum likelihood estimators.
  • The Cramér-Rao lower bound establishes a theoretical limit on the variance of unbiased estimators. Maximum likelihood estimators are significant because they can achieve this lower bound under certain conditions, making them efficient estimators. When MLEs meet this criterion, they represent the best possible estimates for parameters by minimizing variance and thus ensuring precision in statistical inference. This property highlights their value in practical applications across various fields.

Related terms

Likelihood Function: A function that represents the probability of observing the given data under different parameter values of a statistical model.

Sufficient Statistic: A statistic that captures all the information needed from the sample to estimate a parameter, meaning no other statistic can provide additional information about that parameter.

Asymptotic Normality: The property that as the sample size increases, the distribution of the maximum likelihood estimator approaches a normal distribution.