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Applied and theoretical statistics: e.g. statistical inference, regression, time series, multivariate analysis, data analysis, Markov chain Monte Carlo, design of experiments.

1 vote

Maximization of specific Likelihood function

As @Suvrit wrote in a comment, there's not always a solution. We have $$\frac{L'(s)}{L(s)} = \sum_{i\le m} \frac{t_i}{s^2} - \sum_{i>m} \frac{t_i}{s^2}\frac{p_i}{1-p_i} $$ $$=\sum_{i\le m} \frac{t_i}{ …
Bjørn Kjos-Hanssen's user avatar
1 vote

Is it possible to find an asymptotic distribution for the LRT without the ML estimators bein...

Note that the authors are discussing different things (QMLE vs. QLR) when discussing consistent estimator vs. consistent test. The quasi-likelihood of the QLR is discussed on page 1 of the paper. Also …
Bjørn Kjos-Hanssen's user avatar
1 vote

In a coin flip experiment, what if the probability of success has a distribution other than ...

The basic observation is that $$P(\#\ge k)=P(Y_k:=\sum^k X_i\le T)$$ where $X_i$ are your independent Gaussians $N(\mu,\sigma^2)$ (not really an appropriate assumption since they can be negative, but …
Bjørn Kjos-Hanssen's user avatar
5 votes
Accepted

Is a function of complete statistics again complete?

Geometrically, completeness means something like this: if a vector $g(T)$ is orthogonal to the p.d.f. $f_\theta$ of $T$ for each $\theta$, $$\mathbb E_\theta g(T) = \langle g(T),f_\theta\rangle=0$$ th …
Bjørn Kjos-Hanssen's user avatar
1 vote

Constructing a Bernoulli random variable for ratio of Bernoulli weights

One limitation of the von Neumann trick is that you don't know in advance how many samples will be needed. If you limit the number of samples in advance, we can get a negative answer. That is, suppos …
Bjørn Kjos-Hanssen's user avatar
1 vote
Accepted

Why does differencing create wide-sense stationary time series?

I don't know why that is a common practice, but it makes sense in the case of a Brownian motion with drift $X_t=\sigma W_t+\nu t$. Then we have $$ \mathbb E X_{t+1}=\nu(t+1) $$ which is not time invar …
Bjørn Kjos-Hanssen's user avatar
3 votes

Statistical test comparing two relative frequencies

Assume they are four independent beta random variables $X_i$, with means $\mu_i$. Note that the density functions would depend on the observed samples. We could then test the hypothesis that $\mu_ …
Bjørn Kjos-Hanssen's user avatar
1 vote

Probability calculation, system uptime, likelihood of occurence.

I think you would have to assume something about how often the system switches between down and up. If all the downtime occurs in a single block then the probability of the user hitting the system w …
Bjørn Kjos-Hanssen's user avatar
3 votes

Distinguishing between urn probability models

As you point out, the colors observed will have the same distribution with each of these models. Statistical tests involve asking "what is the probability of what is observed according to various …
Bjørn Kjos-Hanssen's user avatar
1 vote

Do all positive distributions on $N$ variables factor pairwise?

Well, the uniform distribution on $\{(0,1,1), (1,0,1), (1,1,0)\} $ does not factor like that, since it would imply $$0=f(1,1,1)=\prod_{i, j} f_{i, j}(1,1)\ne 0,$$ a contradiction. To get a positive e …
Bjørn Kjos-Hanssen's user avatar
4 votes
Accepted

Is there a mistake in Vapnik's "Basic Lemma"?

You're right, it seems. Suppose $X=\{1, -1\}$; $\mu(\{1\})=\mu(\{-1\})=1/2$; $S$ is the power set of $X$; our data sets have just one element each, so that $f(\{1\})$ is either 0 or 1; and $\epsilon …
Bjørn Kjos-Hanssen's user avatar
1 vote

What are some examples of isotrophic sets?

This answer is referring to version 1 of the question. What are some examples of isotrophic sets? and is there a "good" way to describe them? Isotrophic meaning that a random vector X uniform …
Bjørn Kjos-Hanssen's user avatar
1 vote
Accepted

Parameter estimation distribution for hypergeometric distribution

You can use maximum likelihood estimation: https://en.m.wikipedia.org/wiki/Maximum_likelihood_estimation
Bjørn Kjos-Hanssen's user avatar
1 vote

Sum of covariance matrix of products of dependent variables

As a counterexample let $X$ and $Y$ be independent with $E(X)=E(Y)=0$ and let $n$ be even. For each $i$ let $X_{2i}=X$ and $X_{2i+1}=-X$; similarly $Y_{2i}=Y$ and $Y_{2i+1}=-Y$. Then $\sum_{i\ne j}\ …
Bjørn Kjos-Hanssen's user avatar
3 votes

A definite integral related to sample variances of bivariate Gaussians

It seems that Wolfram Alpha understands this integral. Its answers are given in terms of modified Bessel functions of the first kind $I_k$. It seems that the result is, for $A(k,c):=I(n,c)$, with $n …
Bjørn Kjos-Hanssen's user avatar

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