# Questions tagged [estimation]

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### Why is sample standard deviation a biased estimator of $\sigma$?

According to the Wikipedia article on unbiased estimation of standard deviation the sample SD $$s = \sqrt{\frac{1}{n-1} \sum_{i=1}^n (x_i - \overline{x})^2}$$ is a biased estimator of the SD of the ...
7answers
137k views

### Calculating the parameters of a Beta distribution using the mean and variance

How can I calculate the $\alpha$ and $\beta$ parameters for a Beta distribution if I know the mean and variance that I want the distribution to have? Examples of an R command to do this would be most ...
5answers
3k views

### Can the empirical Hessian of an M-estimator be indefinite?

Jeffrey Wooldridge in his Econometric Analysis of Cross Section and Panel Data (page 357) says that the empirical Hessian "is not guaranteed to be positive definite, or even positive semidefinite, for ...
1answer
245 views

### Trying to Estimate Disease Prevalence from Fragmentary Test Results

In response to the spread of COVID-19 disease, all Californians were ordered on 19 March 2020 to stay at home, except for such necessary errands as trips to grocery stores, pharmacies, etc. On 21 ...
3answers
20k views

### What is a Highest Density Region (HDR)?

In statistical inference, problem 9.6b, a "Highest Density Region (HDR)" is mentioned. However, I didn't find the definition of this term in the book. One similar term is the Highest Posterior ...
6answers
56k views

### What is the difference between estimation and prediction?

For example, I have historical loss data and I am calculating extreme quantiles (Value-at-Risk or Probable Maximum Loss). The results obtained is for estimating the loss or predicting them? Where can ...
15answers
9k views

### Why would parametric statistics ever be preferred over nonparametric?

Can someone explain to me why would anyone choose a parametric over a nonparametric statistical method for hypothesis testing or regression analysis? In my mind, it's like going for rafting and ...
1answer
1k views

### Estimating parameters for a binomial

First of all I'd like to precise that I'm not an expert of the subject. Suppose to have two random variables $X$ and $Y$ that are binomial, respectively $X\sim B(n_1,p)$ and $Y\sim B(n_2,p),$ note ...
4answers
13k views

### Internal vs external cross-validation and model selection

My understanding is that with cross validation and model selection we try to address two things: P1. Estimate the expected loss on the population when training with our sample P2. Measure and report ...
3answers
34k views

### Standard deviation of standard deviation

What is an estimator of standard deviation of standard deviation if normality of data can be assumed?
4answers
37k views

### What is the relation between estimator and estimate?

What is the relation between estimator and estimate?
4answers
17k views

### Calculating required sample size, precision of variance estimate?

Background I have a variable with an unknown distribution. I have 500 samples, but I would like demonstrate the precision with which I can calculate variance, e.g. to argue that a sample size of 500 ...
1answer
3k views

### ARMA/GARCH estimation in sequence

I have a time series that shows a nonstationary seasonal autoregressive component as well as known heteroshedasticity. In order to model the series, I have fit a seasonal ARIMA model for the mean with ...
7answers
3k views

### Is there a GLM bible?

Is there consensus in the field of statistics that one book is the absolute best source and completely covering every aspect of GLM - detailing everything from estimation to inference?
2answers
2k views

### Can we reject a null hypothesis with confidence intervals produced via sampling rather than the null hypothesis?

I have been taught that we can produce a parameter estimate in the form of a confidence interval after sampling from a population. For example, 95% confidence intervals, with no violated assumptions, ...
2answers
10k views

### How does a uniform prior lead to the same estimates from maximum likelihood and mode of posterior?

I am studying different point estimate methods and read that when using MAP vs ML estimates, when we use a "uniform prior", the estimates are identical. Can somebody explain what a "uniform" prior is ...
1answer
3k views

### What is an unbiased estimate of population R-square?

I am interested in getting an unbiased estimate of $R^2$ in a multiple linear regression. On reflection, I can think of two different values that an unbiased estimate of $R^2$ might be trying to ...
6answers
5k views

### If a credible interval has a flat prior, is a 95% confidence interval equal to a 95% credible interval?

I'm very new to Bayesian statistics, and this may be a silly question. Nevertheless: Consider a credible interval with a prior that specifies a uniform distribution. For example, from 0 to 1, where 0 ...
1answer
14k views

### Maximum likelihood estimators for a truncated distribution

Consider $N$ independent samples $S$ obtained from a random variable $X$ that is assumed to follow a truncated distribution (e.g. a truncated normal distribution) of known (finite) minimum and maximum ...
1answer
5k views

### Are estimates of regression coefficients uncorrelated?

Consider a simple regression (normality not assumed): $$Y_i = a + b X_i + e_i,$$ where $e_i$ is with mean $0$ and standard deviation $\sigma$. Are the Least Square Estimates of $a$ and $b$ ...
4answers
45k views

### Why squared residuals instead of absolute residuals in OLS estimation? [duplicate]

Why are we using the squared residuals instead of the absolute residuals in OLS estimation? My idea was that we use the square of the error values, so that residuals below the fitted line (which are ...
2answers
12k views

2answers
246 views

### What is the relationship between minimizing prediction error versus parameter estimation error?

With the advent of statistical learning techniques, people are talking a lot about prediction error, while in classical statistics, one is focusing on parameter estimation error. What is the ...
1answer
10k views

### Variance of the reciprocal II

Background I've recently read the paper Leo A. Goodman, On the Exact Variance of Products Journal of the American Statistical Association Vol. 55, No. 292 (Dec., 1960), pp. 708-713 from where I ...
1answer
3k views

### What is the distribution of the variance of a sample from an unknown distribution?

I am sampling from a parameter with unknown distribution. I would like to calculate a 95% CI for the standard deviation of the sample. @cardinal provides a nice general solution for calculating a CI ...
2answers
876 views

### Seasonal adjustment for a series that has already been adjusted

A dataset I am working with (from the OECD), for harmonised unemployment seems to be seasonally adjusted: The unemployment rates shown here are calculated as the number of unemployed persons as a ...
1answer
746 views

### Estimate normal distribution from small sample with rankings

If I have n samples from an $N(\mu,\sigma)$ distribution, how can I estimate the distribution from a subset of m of these n samples where the order within those n is known. For example, if n = 100 ...
6answers
17k views

### How to calculate Zipf's law coefficient from a set of top frequencies?

I have several query frequencies, and I need to estimate the coefficient of Zipf's law. These are the top frequencies: ...
1answer
2k views

### Is the mean (Bayesian) posterior estimate of $\theta$ a (Frequentist) unbiased estimator of $\theta$?

I am wondering about the different ways that Bayesian and Frequentist statistic connect with each other. I recalled that the Maximum Likelihood estimate of a parameter $\theta$ is not necessarily an ...
2answers
9k views

### What are complete sufficient statistics?

I have some trouble understanding complete sufficient statistics? Let $T=\Sigma x_i$ be a sufficient statistic. If $E[g(T)]=0$ with probability 1, for some function $g$, then it is a complete ...
1answer
2k views

### James-Stein Estimator with unequal variances

Every statement I find of the James-Stein estimator assumes that the random variables being estimated have the same (and unit) variance. But all of these examples also mention that the JS estimator ...
1answer
647 views

### Does adjusted R-square seek to estimate fixed score or random score population r-squared?

Population r-square $\rho^2$ can be defined assuming fixed scores or random scores: Fixed scores: The sample size and the particular values of the predictors are held fixed. Thus, $\rho^2_f$ is the ...
1answer
1k views

### Relation Between Bayesian Estimation and Maximum a posteriori estimation

Is maximum a posteriori estimation some kind of Bayesian Estimation? If yes, can you point out other Bayesian estimators? Edit: So I've come to know the following (don't know if they are correct): ...
3answers
1k views

### How to do estimation, when only summary statistics are available?

This is in part motivated by the following question and the discussion following it. Suppose the iid sample is observed, $X_i\sim F(x,\theta)$. The goal is to estimate $\theta$. But original sample ...
3answers
15k views

### Standard error of a ratio

I have a linear regression and two estimates, say A and B and their standard errors. I need to find the standard error of a ratio A/B [or A/(1-B)]. I guess the main problem is that I don't know the ...
4answers
10k views

### How large should a sample be for a given estimation technique and parameters?

Is there a rule-of thumb or even any way at all to tell how large a sample should be in order to estimate a model with a given number of parameters? So, for example, if I want to estimate a least-...