Приклади вживання Posterior distribution Англійська мовою та їх переклад на Українською
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Subsequently, the posterior distribution becomes the next prior.
This is achieved by updating'beliefs' through the use of prior and posterior distribution.
It is often desired to use a posterior distribution to estimate a parameter or variable.
Several methods of Bayesianestimation select measurements of central tendency from the posterior distribution.
It yields a quantile from the posterior distribution, and is a generalization of the previous loss function:.
The relative acceptancefrequencies for the different models now approximate the posterior distribution for these models.
There are many problems where a glance at posterior distributions, for suitable priors, yields immediately interesting information.
Then we simply add in the counts for all the new observations(the vector c) in order to derive the posterior distribution.
In that special case, the prior and posterior distributions were Beta distributions and the data came from Bernoulli trials.
In this section,we will consider a so-called conjugate prior for which the posterior distribution can be derived analytically.
The denominator of the posterior distribution(so-called partition function) does not depend on θ and therefore plays no role in the optimization.
The sequential use of Bayes' formula: when more data become available,calculate the posterior distribution using Bayes' formula;
The posterior distribution should have a nonnegligible probability for parameter values in a region around the true value of in the system, if the data are sufficiently informative.
The sequential use of the Bayes' formula: when more data becomes available,calculate the posterior distribution using the Bayes' formula;
In sequential estimation, unless a conjugate prior is used, the posterior distribution typically becomes more complex with each added measurement, and the Bayes estimator cannot usually be calculated without resorting to numerical methods.
This is because the choice of summary statistics andthe choice of tolerance constitute two sources of error in the resulting posterior distribution.
The usual priors such as the Jeffreys prior often do not work, because the posterior distribution will not be normalizable and estimates made by minimizing the expected loss will be inadmissible.
The method of maximum a posteriori estimation then estimates θ{\displaystyle\theta}as the mode of the posterior distribution of this random variable:.
In fact, if the prior distribution is a conjugate prior,and hence the prior and posterior distributions come from the same family, it can easily be seen that both prior and posterior predictive distributions also come from the same family of compound distributions. .
Assuming θ is distributed according to the conjugate prior, which in this case is the Beta distribution B(a,b), the posterior distribution is known to be B(a+x, b+n-x).
This is both because these estimators are optimal under squared-error and linear-error loss respectively-which are more representative of typical loss functions- and because the posterior distribution may not have a simple analytic form: in this case, the distribution can be simulated using Markov chain Monte Carlo techniques, while optimization to find its mode(s) may be difficult or impossible.
Donald Rubin, when discussing the interpretation of Bayesian statements in 1984[1],described a hypothetical sampling mechanism that yields a sample from the posterior distribution.
The outcome of the ABC rejection algorithm is a sample ofparameter values approximately distributed according to the desired posterior distribution, and, crucially, obtained without the need of explicitly evaluating the likelihood function(Figure 1).
Although Diggle and Gratton's approach had opened a new frontier, their method was not yet exactly identical to what is now known as ABC,as it aimed at approximating the likelihood rather than the posterior distribution.
A conjugate prior is defined as a prior distribution belonging to some parametric family,for which the resulting posterior distribution also belongs to the same family.
This makes a great deal of intuitive sense: if, for example, there are three possible categories, and category 1 is seen in the observed data 40% of the time, one would expect on average tosee category 1 40% of the time in the posterior distribution as well.
The fourth line is simply a rewriting of the third in a different notation,using the notation farther up for an expectation taken with respect to the posterior distribution of the parameters.
Another prescient point was made when Rubin argued that in Bayesian inference, applied statisticians should not settle for analytically tractable models only butinstead consider computational methods that allow them to estimate the posterior distribution of interest.
Now the posterior can be expressed as a normal distribution times an inverse-gamma distribution:.