Questions tagged [multivariate-normal-distribution]
The multivariate normal distribution, is a generalization of the one-dimensional (univariate) normal distribution to higher dimensions. (Also called, multivariate Gaussian)
744 questions
2 votes
0 answers
40 views
Conjugate prior for normal likelihood when the likelihood covariance is shifted
I have a multivariate normal likelihood of the form $$p(y| \mu_\alpha, \Sigma_y + \Sigma_\alpha) = N(\mu_\alpha, \Sigma_y + \Sigma_\alpha) $$ where $y$ is observed data, $\Sigma_y$ is known, and $(\...
2 votes
0 answers
83 views
Change of Variables in a Double Integral Involving Bivariate Normal Sample and Spectral Decomposition
In my research involving statistical inference for the bivariate normal distribution under a special sampling scheme, I encountered the following integral: \begin{eqnarray} I=\int_{-\sqrt{s_{11}}}^{\...
0 votes
0 answers
27 views
Why don't we ignore dividing by variance in discriminant functions for the normal density in case where covariance matrix for all classes is sigma*I?
I am studying about Discriminant Functions For The Normal Density (2.6) from the book Pattern Classification (Second Edition) by Duda,Hart and Stork.The book suggest following function for ...
6 votes
3 answers
286 views
Covariance matrix construction problem for multivariate normal sampling
I have encountered a problem when trying to simulate from a multivariate normal distribution with a covariance matrix built to encode specific correlations. Most of my parameters are estimated from ...
3 votes
1 answer
232 views
Asymmetric Bayes error $\mathcal{N}\left(0,\begin{bmatrix} \sigma_1^2 & 0 \\ 0 & \sigma_2^2 \end{bmatrix}\right)$ vs $\mathcal{N}(0,I)$ classification
Consider the problem of classifying $x \in \mathbb{R}^2$ into one of two classes, $c1$ and $c2$, with known distributions \begin{align} & p(x\mid c1) \sim \mathcal{N}\left(\begin{bmatrix} 0 \\ 0 \...
0 votes
0 answers
51 views
Test the hypothesis $\langle \mu_1,\mu_2\rangle= \langle \mu_3,\mu_4\rangle$ for four $d$-dimensional groups of normal population
Assume that I have four groups of samples, each from a $d$-dimensional normal population $N(\mu_i,\Sigma_i)$ ($1\le i\le 4$). All the $\mu_i, \Sigma_i$ are unknown parameters. I need to test the ...
4 votes
0 answers
158 views
How can we efficiently sample from the truncated multivariate normal distribution? [closed]
As the title says, I would like to know if there any method already implemented in R that efficiently samples from the truncated multivariate normal distribution. More precisely, given $\textbf{X}\sim\...
1 vote
3 answers
168 views
How can we generate a nonstandard multivariate normal from a standard multivariate normal? [duplicate]
Is this true: Let $$Z \sim \mathcal N (0, I).$$ Then if $$X = \Sigma^{1/2}Z + \mu$$ then $$X \sim \mathcal N(\mu, \Sigma).$$ That is, we can nonstandardize a multivariate normal in the exact way we do ...
2 votes
1 answer
200 views
Is the expression for $\mathbb{E}[\textbf{X}\textbf{X}' \mid \textbf{X} \leq \textbf{C}\textbf{b}]$ correct?
As the title says, I would like to know if the following relation is true: \begin{align*} \mathbb{E}[\textbf{X}\textbf{X}' \mid \textbf{X} \leq \textbf{C}\textbf{b}] = \boldsymbol{\Sigma} + \mathbb{E}[...
3 votes
3 answers
272 views
Asymptotic variance of MLE of $\boldsymbol \mu$ when $\lVert \boldsymbol \mu \rVert=1$
Suppose $(X_1,Y_1),\ldots,(X_n,Y_n)$ is a random sample from a bivariate normal $N_2(\boldsymbol \mu, I_2)$ distribution where $\lVert \boldsymbol \mu \rVert=1$. Let $\widehat{\boldsymbol\mu}$ be the ...
2 votes
1 answer
87 views
Difference between normal and multivariate normal distribution for Y in linear regression?
In linear regression, I'm assuming that when $y$ belongs to a normal distribution it's because there's only one variable, as in it's a simple linear regression, for example $y = \beta_{0} + \beta_1 ...
0 votes
0 answers
115 views
Non-monotonic function preserving Gaussian distribution
I'm interested in knowing whether the following statement is true, and if it's false, what condition should be satisfied on $f$: If $x \in \mathbb R^m$ and $y = f(x) \in \mathbb R^n$ follow two (...
5 votes
0 answers
59 views
Correlation of estimated rates for overlapping composite endpoints from the same study
Background Often we have multiple composite endpoints reported from the same clinical trial. Let's say we have the hazard rate per 100 patient-years reported (in a publication, we don't have the raw ...
1 vote
0 answers
103 views
Independence of Principal Components
Okay, here is the scenario. We have a bunch of data, say x1,...,x300 that we have collected for a bunch of samples, y1,...,y1000. The data x1,...,x300 is dependent (value of x1 is correlated to the ...
2 votes
0 answers
62 views
Cholesky factorization of a conditional multivariate normal distribution
Let $X$ be a random vector with multivariate normal distribution: $X\sim \mathcal{N}(\mu,\Sigma)$. Let $L$ be the Cholesky factorization of $\Sigma$: $\Sigma = LL'$, so that we can write $$X=L X_0 +\...