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  2. Degrees of freedom (statistics) - Wikipedia

    en.wikipedia.org/wiki/Degrees_of_freedom...

    Mathematically, the first vector is the oblique projection of the data vector onto the subspace spanned by the vector of 1's. The 1 degree of freedom is the dimension of this subspace. The second residual vector is the least-squares projection onto the (n1)-dimensional orthogonal complement of this subspace, and has n1 degrees of freedom.

  3. Chi-squared distribution - Wikipedia

    en.wikipedia.org/wiki/Chi-squared_distribution

    Because the square of a standard normal distribution is the chi-squared distribution with one degree of freedom, the probability of a result such as 1 heads in 10 trials can be approximated either by using the normal distribution directly, or the chi-squared distribution for the normalised, squared difference between observed and expected value.

  4. Proofs related to chi-squared distribution - Wikipedia

    en.wikipedia.org/wiki/Proofs_related_to_chi...

    Here is one based on the distribution with 1 degree of freedom. Suppose that X {\displaystyle X} and Y {\displaystyle Y} are two independent variables satisfying X ∼ χ 1 2 {\displaystyle X\sim \chi _{1}^{2}} and Y ∼ χ 1 2 {\displaystyle Y\sim \chi _{1}^{2}} , so that the probability density functions of X {\displaystyle X} and Y ...

  5. Degrees of freedom (physics and chemistry) - Wikipedia

    en.wikipedia.org/wiki/Degrees_of_freedom_(physics...

    The term involving the product of X 1 and X 2 is a coupling term that describes an interaction between the two degrees of freedom. For i from 1 to N, the value of the i th degree of freedom X i is distributed according to the Boltzmann distribution. Its probability density function is the following:

  6. Degrees of freedom (mechanics) - Wikipedia

    en.wikipedia.org/wiki/Degrees_of_freedom_(mechanics)

    The position of an n-dimensional rigid body is defined by the rigid transformation, [T] = [A, d], where d is an n-dimensional translation and A is an n × n rotation matrix, which has n translational degrees of freedom and n(n1)/2 rotational degrees of freedom.

  7. Noncentral chi-squared distribution - Wikipedia

    en.wikipedia.org/wiki/Noncentral_chi-squared...

    We've assumed, without loss of generality, that , …, are standard normal, and so + + has a central chi-squared distribution with (k − 1) degrees of freedom, independent of . Using the poisson-weighted mixture representation for X 1 2 {\displaystyle X_{1}^{2}} , and the fact that the sum of chi-squared random variables is also a chi-square ...

  8. Student's t-distribution - Wikipedia

    en.wikipedia.org/wiki/Student's_t-distribution

    Density of the t distribution (red) for 1, 2, 3, 5, 10, and 30 degrees of freedom compared to the standard normal distribution (blue). Previous plots shown in green. 1 degree of freedom

  9. Noncentral chi distribution - Wikipedia

    en.wikipedia.org/wiki/Noncentral_chi_distribution

    A noncentral chi distribution with 2 degrees of freedom is equivalent to a Rice distribution with =. If X follows a noncentral chi distribution with 1 degree of freedom and noncentrality parameter λ, then σX follows a folded normal distribution whose parameters are equal to σλ and σ 2 for any value of σ.