MHB Derivation of snedecors F distribution

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The F distribution is derived from the ratio of two independent chi-squared variables, specifically when X1 follows a chi-squared distribution with n1 degrees of freedom and X2 with n2 degrees of freedom. The relationship is expressed as (X1/n1) / (X2/n2) following an F distribution with parameters n1 and n2. The moment-generating function (mgf) can be utilized to find the raw moments of the F distribution. Additionally, the mean and variance can be calculated, with the mean being n2 / (n2 - 2) for n2 > 2, and the variance being [2n2^2(n1 + n2 - 2)] / [n1(n2 - 2)^2(n2 - 4)] for n2 > 4. This derivation and properties are crucial for statistical analysis involving the F distribution.
coolamko12
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derive f distribution as x1 and x2 are independent random variables having a chi-square distribution with n1 and n2 degrees of freedom.. aslo mgf and find raw moments ... and finds its mean and variance.?prove it ?help me guys?
 
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coolamko12 said:
derive f distribution as x1 and x2 are independent random variables having a chi-square distribution with n1 and n2 degrees of freedom.. aslo mgf and find raw moments ... and finds its mean and variance.?prove it ?help me guys?

There's a theorem which states that the $F$ distribution can be defined as the fraction of two independent chi-squared distributions. More precisely,

If $X_1 \sim \chi_{n_1}^2$ and $X_2 \sim \chi_{n_2}^2$ are two independent chi-squared distributions then $\frac{X_1/n_1}{X_2/n_2} \sim F(n_1,n_2)$.
 
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