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In probability theory and statistics, the exponential distribution or negative exponential distribution is the probability distribution of the distance between events in a Poisson point process, i.e., a process in which events occur continuously and independently at a constant average rate; the distance parameter could be any meaningful mono-dimensional measure of the process, such as time ...
The probability distribution function (and thus likelihood function) for exponential families contain products of factors involving exponentiation. The logarithm of such a function is a sum of products, again easier to differentiate than the original function.
Consider the problem of estimating the rate parameter, λ of the exponential distribution which has the probability density function: (;) = {,,, <Suppose that a sample of data is available from which either the sample mean, ¯, or the sample median, m, can be calculated.
A textbook example is parameter estimation of a probability distribution function.Consider the exponential distribution: =,, >The hypotheses are {: =: = >.Then the log-likelihood function (LLF) for one sample is
In statistics, maximum likelihood estimation (MLE) is a method of estimating the parameters of an assumed probability distribution, given some observed data.This is achieved by maximizing a likelihood function so that, under the assumed statistical model, the observed data is most probable.
A likelihood function arises from a probability density function considered as a function of its distributional parameterization argument. For example, consider a model which gives the probability density function f X ( x ∣ θ ) {\displaystyle \;f_{X}(x\mid \theta )\;} of observable random variable X {\displaystyle \,X\,} as a function of a ...
An alternative derivation of the maximum likelihood estimator can be performed via matrix calculus formulae (see also differential of a determinant and differential of the inverse matrix). It also verifies the aforementioned fact about the maximum likelihood estimate of the mean. Re-write the likelihood in the log form using the trace trick:
When considered a function of n for fixed m this is a likelihood function. L ( n ) = [ n ≥ m ] n {\displaystyle {\mathcal {L}}(n)={\frac {[n\geq m]}{n}}} The maximum likelihood estimate for the total number of tanks is N 0 = m , clearly a biased estimate since the true number can be more than this, potentially many more, but cannot be fewer.