Questions tagged [posterior]

Refers to the probability distribution of parameters conditioned on data in Bayesian statistics.

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14 views

Is it valid to use samples drawn from posterior using MCMC as prior distribution in sequational updating?

Let's say there are two sets of parameters $x$ and $y$, and two sets of data $a$ and $b$. $x$ only depends on $a$, but $y$ depends on both $a$ and $b$. I first sample from the posterior $$P(x \mid a) ...
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Notation in definition of a quantity involving uncertainty and posterior probability

As a probs & stats noob, I'm still getting confused by notation. I would appreciate if someone could elaborate a bit on what's going on here, on p12 of Settles' Active Learning survey (2012). He ...
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Comparing posteriors when the same data are examined with different priors

I have two Bayesian regression models: both use the same data $D$ and all same specification $M$ but the different priors $p_1(\theta)$ and $p_2(\theta)$. Can I interpret the posteriors from the two ...
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Poisson-gamma posterior mean expectation

Let's have a gamma prior $\lambda\sim \operatorname{Gamma}(a,b)$ (mean: $\frac{a}{b}$) With Poisson data $Y\mid \lambda\sim \operatorname{Pois}(N\lambda)$ (mean: $N\lambda$) The posterior is $\...
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What is the posterior mean of $\mu$ given a randomly stopped i.i.d. observations from a Normal

Let's imagine I have a machine giving me an independent random number from a normal distribution $N(\mu,1)$ whenever I push a button. I have a stopping rule to decide how many samples to collect - I ...
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Residual Analysis

I have just reproduced an example regarding a regression model for fibre strength data. The data consisted of tensile strengths of silicon carbide fibre at four different lengths. From the data, a ...
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1answer
21 views

meaning of posterior distribution and credible internal

In Bayesian method, we can get a posterior distribution of a parameter. Now I want to do some simulation to know if the posterior distribution is the same as the true distribution. For example, mean ...
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22 views

The posterior distribution of Bt is Bernoulli

I'm trying to follow the math of Estimating Heston's and Bates’ models parameters using Markov chain Monte Carlo simulation in Journal of Statistical Computation and Simulation, but I'm having trouble ...
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how posterior function is calculated in JAGS

I have a theoretical question. I understand the JAGS samples from the posterior function of a model. But I don't understand (nor I can find in the documentation) how it calculates the posterior in the ...
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Bayesian Estimation of a Mean and Standard Deviation (2D)

(Originally Posted at: https://stackoverflow.com/questions/56399700/bayesian-estimation-of-a-mean-and-standard-deviation-2d) I'm currently following Think Bayes, an introductory text to Bayesian ...
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Is a Bayesian posterior kind of like the marginal distribution of a frequentist estimator?

I've been thinking a lot about the relationships between various concepts like hypothesis testing, posterior distributions, and estimators. If I understand correctly, a frequentist estimator $\hat\...
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Is it rational to select a parameter posterior value because it maximizes utility, even if probability is low?

I did Bayesian parameter estimation and I have now an estimate of the posterior distribution for my model parameters (say I have 2000 samples). Now I would like to make the optimal decision under my ...
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23 views

Calculating the posterior distribution of linear predictor

I am currently fitting a linear regression model in a bayesian framework in R with the package ngspatial. To investigate the quality of fit, I would like to calculate the bayes R2, as suggested here ...
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21 views

Posterior convergence in expectation vs probability

Let's assume that we are doing approximate Bayesian inference and compute the convergence of our posterior estimate to the true value of the parameter using Wasserstein distance. Why posterior ...
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Finding the mode of the posterior distribution

I have the following hierachical bayesian model - $\mathbf{x}|\mathbf{c},\sigma^2 \sim \mathcal{N}(\mathbf{x}|\mathbf{c},\sigma^2)$ $\mathbf{c}|\mathbf{c}_1,\sigma^2_2 \sim \mathcal{N}(\mathbf{c}|\...
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Marginalising over Dependent Random Variables

Suppose I have two RVs, $A$, and $B$. Every place I have looked thus far suggests the following for marginalisation, which for me is fine: $f_A(a) = \int_{-\infty}^{\infty} f_{A,B}(a,b)db $. ...
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Generating data from the posterior distribution

Let $$p(D \mid \mu,\sigma^2) \sim \mathcal{N}(\mu,\sigma^2)$$ where $D=(x_1\ldots x_n)$ is my data. I imposed a normal prior on the mean as $$\pi(\mu) \sim \mathcal{N}(\mu_0,\sigma_0^2)$$ Using Bayes, ...
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dirichlet distribution and excessively large numerator

what I am trying to do is calculating posterior probability using dirichlet distribution as my prior. the situation is like this. a web log have three variables A, B, C, and each variable's value is ...
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Posterior using Numerical integration - why divided by (sum of posterior / number of samples)

Background Reading Markov Chain Monte Carlo (MCMC) and the numerical integration method to get the posterior. Question The implementation code divides the posterior with (post.sum() / len(thetas)). ...
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Finding the posterior distribution of a Bayesian analysis prior

I have a prior distribution $f(x)=\pi cos(\pi x) $ where $x$ is the probability of getting tails in a coin toss. Should a coin toss result in tails, how would this be reflected in the posterior ...
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Finding the posterior distribution for Beta likelihood with unknown alpha [duplicate]

If $(y_i|\theta)$ is distributed as $Beta(y_i,\theta,\beta)$ then what prior distribution do I use? My initial thought was to use a Beta prior. Is this right? I found the likelihood but I'm not sure ...
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What mathematically enables one to Bayesian update multiple times?

I'm going through the MIT OCW notes on probability and statistics and came across an example in some class notes where the posterior is updated after two events: $x_1 = 1$ and $x_2=1$, which ...
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How do we reuse and store the output of an MCMC?

For many Bayesian models, the posterior distribution is intractable... a solution is then to sample points from this unknow distribution with a Markov Chain Monte Carlo (MCMC). But at the end, how do ...
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Explanation of the Posterior Derivation of the Gaussian Distribution

I'm reading through my notes and I don't quite understand this bit: I understand how the likelihood was calculated but no more than that.Can anyone explain the steps and exactly how they go from one ...
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Bayesian Inference, Posteriors Priors and Likelihoods [duplicate]

So at the moment I'm reading through my notes on Bayesian Inference and I'm really just not understanding anything. If anyone has any good websites that explain this topic well then I'd be really ...
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Constraints on choice of marginal distribution and likelihood

For some time I have been reading into Bishop's Pattern Recognition and Machine Learning. Coming back to some earlier chapters the following got me confused and I am interested where, formally I go ...
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1D Bayesian Inference clarification

I'd like some help making sure I understand a 1D Bayesian inference problem. Say I have a data vector which is an array of the number of flu cases reported weekly in California for the past 10 years. ...
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Closed form posterior for product of inverse Gamma and Normal distribution

I am currently reading a book about mixture analysis, and in the textbook a posterior for the parameters $\mu1,\mu2,\sigma_1^2,\sigma_2^2$ of a two-component gaussian mixture is derived as follows (S ...
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Posterior probability with Bins

For the following question I wanted to know how to estimate the probability that I have selected from bin A. There are 10 bins, 4 are labelled A, 6 labelled B. Each bin has balls with two colors (Red/ ...
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23 views

Setting an upper limit on an estimate

I have used MCMC to estimate the value of a parameter $\theta$ from some data. I have thousands of samples from the (marginal) posterior distribution. The distribution of $\theta$ is roughly Normally ...
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25 views

Finding a posterior distribution from a Poisson likelihood function and a uniform prior distribution

If a counting experiment gives one observation $x=5$, and if the prior distribution is given as a uniform function, then is the following a correct way of calculating the posterior function? First, ...
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Monte Carlo integration for Bayesian parameter estimation

I want to determine the credible interval of a quantity $\theta_1$. I want to make this estimate using observed data by assuming a certain model which depends on $\theta_1$ as well as about n=15 ...
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What is the posterior distribution of a Bernoulli prior that gets updated with a continuous uniform signal?

I'm trying to figure out what the distribution of the posterior is after I update a Bernoulli prior with a continuous uniform signal, say: P(D=G|u)=x where D{G,I} and u is uniformly distributed on ...
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In Bayesian inference, why are some terms dropped from the posterior predictive?

In Kevin Murphy's Conjugate Bayesian analysis of the Gaussian distribution, he writes that the posterior predictive distribution is $$ p(x \mid D) = \int p(x \mid \theta) p(\theta \mid D) d \theta $$ ...
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Model selection for this model with one observation

I would like to perform model selection given a range of $k$ models $\mathcal{M}_1, \mathcal{M}_2, ..., \mathcal{M}_k$, each with some prior probability $f(\mathcal{M}_1), \dots, f(\mathcal{M}_k).$ ...
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1answer
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computing the distribution over the latent function values with the form of a GP predictive

If we have a latent state space $\mathbf{X}$ and the observations $\mathbf{Y}$ and the transition function between two states $\mathbf{x}_{t-1}$ and $\mathbf{x}_{t}$ is given by $\mathbf{f}$ which is ...
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419 views

Joint posterior for finite mixture with normal components

I currently read the book Finite Mixture and Markov Switching Models by Sylvia Frühwirth-Schnatter and I have a question regarding Section 6.2.1 regarding finite mixtures with normal components. Maybe ...
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Full (approximated) posterior covariance matrix - GPML toolbox

I am trying to implement the paper "Streaming Sparse Gaussian Process Approximations" by - Thang D. Bui, Cuong V. Nguyen, Richard E. Turner in matlab. As a start, I create a sparse GP using the GPML ...
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578 views

importance sampling from posterior distribution in R

Today I read that Importance Sampling can be used to draw posterior distribution samples just like Rejection Sampling. However, my understanding of Importance Sampling is that its main purpose is to ...
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1answer
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Conditional Posterior Distributions

So I'm trying to find the conditional posterior distributions of n given $\theta$ and x as well as $\theta$ given n and x. These are my priors (poisson and beta) \begin{equation*} \begin{aligned} &...
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Finding MAP estimate

I think after all the reading I've done I still don't fully understand MAP estimation. I came across a problem that's leaving me dumbfounded. Suppose $A$ ~ $N(0,\sigma^2_1) $ and $\epsilon$ ~ $N(0,\...
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Finding mode of posterior using Newton method in R

I am attempting to approximate the posterior $\tilde{\pi_{G}}(z|\theta,Y)$ which is the Gaussian approximation to the full conditional of $z$, and in order to do this I need to find the mode $z^{*} \...
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Posterior predictive check for capture-recapture data using jagsUI wrapper

The R package jagsUI is a wrapper for JAGS that has some awesome functions, including a posterior predictive check. As discussed here, you simulate the new data for the parameters based on the ...
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51 views

Bayesian updating with multiple priors and multiple likelihood functions

$\Omega$ (finite) state space, $S$ (finite) signal space. Suppose we have a closed and convex set of priors $\mathcal{M}\subseteq \Delta(\Omega)$ such that each of them has full support. Let $\...
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1answer
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Posterior density for a linear regression model

Given a classical linear regression model $$y = X\beta + \varepsilon,$$ $$\varepsilon\sim N(0,\sigma^2I_n),$$ the posterior density is proportional to the product of the likelihood and the selected ...
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Computing posterior density of Normal with unknown $\mu$ and $\sigma^2$

(From Bayesian Essentials with R by Marin & Robert page 31) We are given an iid sample $\mathfrak{D}_n = (x_1, \dots, x_n)$ from the normal distribution $\mathcal{N}(0, \sigma^2)$ and $\theta=(\...
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Bayes: posterior density, mean and mode [duplicate]

The likelihood function is $f(n_1|\alpha,n) = [\frac{n!}{n_1!(n-n_1)!}]\alpha^{n_1}(1-\alpha)^{n-n_1}$ The prior for $\alpha$ $g(\alpha)=(\alpha(1-\alpha))^{-1}$ for $\alpha$ between 0 and 1. ...
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In a Bayesian MCMC model, if we plug the average of posterior draws back into the Likelihood, would it be estimating the Posterior Predictive?

Suppose we have a Bayesian model with data $y$ and a parameter to be estimated, $\theta$. Then the posterior is written as: $$ p(\theta | y) \propto p(y|\theta)p(\theta) $$ Suppose that we used an ...
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How do I calculate a Bayesian Posterior Distribution from an Exponential Prior and Sample Data

I have a dataset where each observation is a length of time (e.g. 50 days, 70 days, 105 days) and I am trying to utilize Bayesian statistics to calculate a posterior distribution in light of new data. ...
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Calculate a Bayesian 'posterior predictive p-value' for a multinomial logistic regression

For assessing the fit of a model in a Bayesian framework, 'posterior predictive p-values' (PPPs) are often used. Here, a value close to 0.5 indicates a good fit; a value close to 0 or 1 indicates a ...