Let Y1, Y2, Y3, Y4 ~ N(βο, σ²), Y's independent.
Given the vector Y4×1 = [Y1, Y2, Y3, Y4]T and the orthonormal
coordinate system U₁ = [1, 1, 1, 1]T, U2 = [1, 1, -1, -1]T,
U3 = [1, -1, 1, -1]T, and U4 = [1, -1,-1,1]T.
First, find C1, C2, C3, C4 for which
Y = C1U1 + C2U2 + C3U3 + C4U4.
The distribution of
$$ \frac{c_1^2 + c_2^2 + c_3^2 + c_4^2}{\sigma^2} $$
is
F distribution
T distribution
Chi-square
Normal