Quadratic Form (statistics) - Examples of Quadratic Forms

Examples of Quadratic Forms

In the setting where one has a set of observations and an operator matrix, then the residual sum of squares can be written as a quadratic form in :

For procedures where the matrix is symmetric and idempotent, and the errors are Gaussian with covariance matrix, has a chi-squared distribution with degrees of freedom and noncentrality parameter, where

may be found by matching the first two central moments of a noncentral chi-squared random variable to the expressions given in the first two sections. If estimates with no bias, then the noncentrality is zero and follows a central chi-squared distribution.

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