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  2. Orthogonal polynomials - Wikipedia

    en.wikipedia.org/wiki/Orthogonal_polynomials

    It induces a notion of orthogonality in the usual way, namely that two polynomials are orthogonal if their inner product is zero. Then the sequence ( P n ) ∞ n =0 of orthogonal polynomials is defined by the relations deg ⁡ P n = n , P m , P n = 0 for m ≠ n . {\displaystyle \deg P_{n}=n~,\quad \langle P_{m},\,P_{n}\rangle =0\quad {\text ...

  3. Contrast (statistics) - Wikipedia

    en.wikipedia.org/wiki/Contrast_(statistics)

    A contrast is defined as the sum of each group mean multiplied by a coefficient for each group (i.e., a signed number, c j). [10] In equation form, = ¯ + ¯ + + ¯ ¯, where L is the weighted sum of group means, the c j coefficients represent the assigned weights of the means (these must sum to 0 for orthogonal contrasts), and ¯ j represents the group means. [8]

  4. Uncorrelatedness (probability theory) - Wikipedia

    en.wikipedia.org/wiki/Uncorrelatedness...

    If two variables are uncorrelated, there is no linear relationship between them. Uncorrelated random variables have a Pearson correlation coefficient, when it exists, of zero, except in the trivial case when either variable has zero variance (is a constant). In this case the correlation is undefined.

  5. Orthogonality principle - Wikipedia

    en.wikipedia.org/wiki/Orthogonality_principle

    In the special case of linear estimators described above, the space is the set of all functions of and , while is the set of linear estimators, i.e., linear functions of only. Other settings which can be formulated in this way include the subspace of causal linear filters and the subspace of all (possibly nonlinear) estimators.

  6. Instrumental variables estimation - Wikipedia

    en.wikipedia.org/wiki/Instrumental_variables...

    In this case, it is valid to use the estimates to predict values of y given values of X, but the estimate does not recover the causal effect of X on y. To recover the underlying parameter β {\displaystyle \beta } , we introduce a set of variables Z that is highly correlated with each endogenous component of X but (in our underlying model) is ...

  7. Hermite polynomials - Wikipedia

    en.wikipedia.org/wiki/Hermite_polynomials

    Since the power-series coefficients of the exponential are well known, and higher-order derivatives of the monomial x n can be written down explicitly, this differential-operator representation gives rise to a concrete formula for the coefficients of H n that can be used to quickly compute these polynomials.

  8. Canonical correlation - Wikipedia

    en.wikipedia.org/wiki/Canonical_correlation

    In statistics, canonical-correlation analysis (CCA), also called canonical variates analysis, is a way of inferring information from cross-covariance matrices.If we have two vectors X = (X 1, ..., X n) and Y = (Y 1, ..., Y m) of random variables, and there are correlations among the variables, then canonical-correlation analysis will find linear combinations of X and Y that have a maximum ...

  9. Response surface methodology - Wikipedia

    en.wikipedia.org/wiki/Response_surface_methodology

    Orthogonality The property that allows individual effects of the k-factors to be estimated independently without (or with minimal) confounding. Also orthogonality provides minimum variance estimates of the model coefficient so that they are uncorrelated. Rotatability The property of rotating points of the design about the center of the factor ...