# Questions tagged [definition]

This tag indicates questions about definitions of statistical terms. Use a more general tag [terminology] for questions on statistical parlance that are not specifically about definitions.

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### What is the correct definition of the correlation of two random variables?

In the book Signal Processing for Communications by Prandoni and Vetterli, correlation of two variables is defined as the expected value of their product, while the covariance is refered to as the &...
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### "observational study vs experiment" why is the answer of the question "experiment " and not "observational study"?

this will be on my exam and i'm indignation to have such confusing/vague questions "validating" my results (explaining me why it is not "confusing/vague" and make me look like a ...
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### is the definition of "observational study" wrongly elaboreted?/ observational study vs experiment

Google. "An observational study observes individuals and measures variables of interest but does not attempt to influence the responses" Question that made me have an argument with my ...
1 vote
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### What is the concept of limiting event? [duplicate]

Would any member of Cross validated stack exchange prove highlighted 1 and 2 by simple and clear explanation with examples? My answers: A sequence of events {$E_n, n\geq 1$} is said to be an ...
1 vote
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### Do we really know what does probability mean? [closed]

When I read debates or listen to videos about probabilities and bayesians versus frequentists, it reminds me like a lot the question of "do we know what infinite means?" (related to the ...
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### What does it mean that the hypothesis space does not contain the target concept?

I read that the algorithm candidate elimination would not converge if the Hypothesis space $H$ does not contain the target concept. You can look it up here. I quoted from the 5th heading: The ...
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### Why do we call an assignment mechanism unconfounded assignment mechanism?

Consider some experiment with $n$ units along outcomes $Y=(Y_1,\dots, Y_n)$, covariates $X=(X_1,\dots, X_n)$ and treatment vector $W=(W_1,\dots, W_n)$ where $Y_i=(Y_i^1,Y_i^0)$ for treatment and ...
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### What is the difference between a census and a parameter in statistics?

I'm going through my class textbook and the definition for a census is When desired information is available for all objects in the population, we have what is called a census. I remember from ...
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### Are there classifiers with infinite number of classes?

I am writing something about time series classification and wrote the following: A classifier is a function that for given input $x_1, ..., x_n$ (in this case representing data stored in audio file) ...
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### Can weak-learner be defined in the case of regression problem?

weak-learner is often defined relating to PAC learning. However, to the extent I know, I have never seen the definition of weak-learner when regression. That is, the definition of weak-learner on ...
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### Bayesian definition of sufficient statistics

Some time ago I wrote a question about what I think/thought (up to my understanding) is an ambiguity of the common definition of sufficient statistics : Conditioning in the definition of sufficient ...
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### Time-series correlation if t is negatively correlated with t+1, t+2... but t+1, t+2... are positively correlated

What kind of time-series correlation are we talking about if t is negatively correlated with t+1, t+2, t+3,... but t+1, t+2, t+3,... are positively correlated? So for example, a positive value in t ...
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### Definition of Corrected Contingency Coefficient

I quote RACHEV, HÖCHSTÖTTER, FABOZZI, FOCARDI (2010). Starting from the bivariate variable $(x,y)$, with the component variable $x$ taking values in $(v_i, i=1,\dots,r)$ and the component variable $y$ ...
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### Doubt around Covariance definition

Given the general definition of Covariance between two random variables $x$ and $y$: \begin{equation*} \text{Cov}(x,y)=\frac{1}{n}\sum_{i=1}^n(x_i-\bar{x})(y_i-\bar{y}) \end{equation*} Does the above ...
1 vote
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### Data appear in both dependent and independent variable: what is this error called?

I want to find a proper name for the analytical problem I've identified below. One of the most accurate measure of firearm availability is the proportion of suicides committed with firearms, or FS/S (...
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### Sequence of random variables vs random sample

I am studying convergence theorems and consistency for estimators. I am confused on the difference between a sample of random variables and a sequence of random variables. Can someone explain the ...
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### Criteria to be called a random variable?

I've read that to call something a random variable, that thing must be the result of a statistical experiment. So it got me thinking in which situations might we have an actual bias? For example, ...
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### What is the definition of a domain in machine learning?

I have been recently doing a lot of reading into statistical tests for comparing models and I've been coming across the term "domain" and phrases like "domain specific learning" a ...
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### Suitable definition of breakdown point for estimators of bounded statistics (i.e constrained estimation)

Let $\Theta$ be a nonempty compact subset of $\mathbb R^d$. For example, the reader may think of the closed unit-ball $\Theta := \{\theta \in \mathbb R^d \mid \|\theta\|_2 \le 1\}$. Consider an ...
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### Intuition about the definition of random variables? [duplicate]

I have been struggling a bit with the definition of random variables, as it seems to me a bit of an amorphous concept connected to quite a few different ideas. The Wikipedia article also didn't clear ...
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### A formal definition of a "measure of association"

I've been trying to come up with a formal definition for a 'measure of association'. An intuitive definition might be something along the lines of 'a function that tells you about the existence or ...
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### What's the difference between mixed effects logit model and mixed logit model?

Recently，I'm working on a dataset with binary responses. I come across two models with quite similar names, i.e., mixed-effects logit model and mixed logit model. As far as I know, the mixed-effects ...
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### Symbol interpretation in non-constant power law density

I am reading Barabasi book on network science. I am struggling to interpret the density formula for a power-law degree distribution with low-degree saturation and high-degree cut-off (http://...
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