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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. Special right triangle - Wikipedia

    en.wikipedia.org/wiki/Special_right_triangle

    Set square shaped as 45° - 45° - 90° triangle The side lengths of a 45° - 45° - 90° triangle 45° - 45° - 90° right triangle of hypotenuse length 1.. In plane geometry, dividing a square along its diagonal results in two isosceles right triangles, each with one right angle (90°, ⁠ π / 2 ⁠ radians) and two other congruent angles each measuring half of a right angle (45°, or ...

  4. 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 ...

  5. Exact trigonometric values - Wikipedia

    en.wikipedia.org/wiki/Exact_trigonometric_values

    The values of sine and cosine of 30 and 60 degrees are derived by analysis of the equilateral triangle. In an equilateral triangle, the 3 angles are equal and sum to 180°, therefore each corner angle is 60°. Bisecting one corner, the special right triangle with angles 30-60-90 is obtained.

  6. Reduced chi-squared statistic - Wikipedia

    en.wikipedia.org/wiki/Reduced_chi-squared_statistic

    The degree of freedom, =, equals the number of observations n minus the number of fitted parameters m. In weighted least squares , the definition is often written in matrix notation as χ ν 2 = r T W r ν , {\displaystyle \chi _{\nu }^{2}={\frac {r^{\mathrm {T} }Wr}{\nu }},} where r is the vector of residuals, and W is the weight matrix, the ...

  7. Noncentral chi-squared distribution - Wikipedia

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

    Suppose that a random variable J has a Poisson distribution with mean /, and the conditional distribution of Z given J = i is chi-squared with k + 2i degrees of freedom. Then the unconditional distribution of Z is non-central chi-squared with k degrees of freedom, and non-centrality parameter .

  8. Chi-squared per degree of freedom - Wikipedia

    en.wikipedia.org/?title=Chi-squared_per_degree...

    Pages for logged out editors learn more. Contributions; Talk; Chi-squared per degree of freedom

  9. 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 ...