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  2. 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.

  3. 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 ...

  4. Bartlett's test - Wikipedia

    en.wikipedia.org/wiki/Bartlett's_test

    The test procedure due to M.S.E (Mean Square Error/Estimator) Bartlett test is represented here. This test procedure is based on the statistic whose sampling distribution is approximately a Chi-Square distribution with ( k − 1) degrees of freedom, where k is the number of random samples, which may vary in size and are each drawn from ...

  5. Rayleigh distribution - Wikipedia

    en.wikipedia.org/wiki/Rayleigh_distribution

    The chi distribution with v = 2 is equivalent to the Rayleigh Distribution with σ = 1: . If R ∼ R a y l e i g h ( 1 ) {\displaystyle R\sim \mathrm {Rayleigh} (1)} , then R 2 {\displaystyle R^{2}} has a chi-squared distribution with 2 degrees of freedom: [ Q = R ( σ ) 2 ] ∼ σ 2 χ 2 2 . {\displaystyle [Q=R(\sigma )^{2}]\sim \sigma ^{2 ...

  6. Chi distribution - Wikipedia

    en.wikipedia.org/wiki/Chi_distribution

    The chi distribution has one positive integer parameter , which specifies the degrees of freedom (i.e. the number of random variables ). The most familiar examples are the Rayleigh distribution (chi distribution with two degrees of freedom ) and the Maxwell–Boltzmann distribution of the molecular speeds in an ideal gas (chi distribution with ...

  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. Degrees of freedom (statistics) - Wikipedia

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

    Here, the degrees of freedom arises from the residual sum-of-squares in the numerator, and in turn the n − 1 degrees of freedom of the underlying residual vector {¯}. In the application of these distributions to linear models, the degrees of freedom parameters can take only integer values.

  9. Pearson's chi-squared test - Wikipedia

    en.wikipedia.org/wiki/Pearson's_chi-squared_test

    The degrees of freedom are not based on the number of observations as with a Student's t or F-distribution. For example, if testing for a fair, six-sided die, there would be five degrees of freedom because there are six categories or parameters (each number); the number of times the die is rolled does not influence the number of degrees of freedom.