# Questions tagged [quadratic-form]

A quadratic form is a homogeneous polynomial of order two.

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### Problem on quadratic form [migrated]

Show that $\{x : x^{T}Ax \le 1\}$ is bounded if $A$ is positive definite, where $x^T=[x_1,x_2,...,x_n]$ and $A$ is an $n\times n$ matrix.
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### Regression: Why does using quadratic expressions work with linear estimators? [duplicate]

My questions is, that I see people using R´s lm() (linear regression model) with Y ~ X^2 e.g. here: Simple non-linear regression problem But I dont see how and ...
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### Maximal inequality for quadratic forms as functions of matrices?

In general, an $M$-estimator is defined as a maximizer of some objective function $Q_n(\theta)$: $\hat{\theta} = \arg\max_{\theta} Q_n(\theta)$. Suppose that $q(\theta) = E Q_n(\theta)$ is uniquely ...
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### Modeling approach to showing a parabolic effect is greater than that expected by scale boundaries

I have conducted an experiment where raters rate different nations on a DV. Each observation is a different nation. I calculated a mean and SD of the DV for each nation. The data we are working with ...
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### Asymptotic normality of quadratic form?

Let $X$ be a $p$-dimensional vector that is asymptotically normal such that $$\sqrt{n}(X - \mu_X) \stackrel{d}\longrightarrow N(0, \Sigma)$$, and let $H$ be a random $p\times p$ symmetric matrix, ...
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### How to include an interaction with a quadratic term? [closed]

I want to predict $y$ with $x_{1}$ and $x_{2}$ and I suppose that $x_{2}$ has a quadratic effect on $y$ and that there is an interaction. How to model that? I've look in previous questions but there ...
1answer
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### Quadratic term of standardized predictor in logistic regression

A random intercept logistic regression is performed to assess the association between $Y$: Disease (Yes/No) and Standardized Predictor($X_1$) adjusting for control variables ($X_2$, $X_3$) based on ...
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### How can I interpret coefficients of quadratic and linear term?

It may be a basic statistic question for someone, but I'm struggling with this. I'm trying to interpret a regression analysis. Here is examples. ...