AbstractLetXbe a normally distributedp‐dimensional column vector with mean μ and positive definite covariance matrix σ. and letXα, α = 1,…,N, be a random sample of sizeNfrom this distribution. PartitionXas (X1,X(2)',X'(3))', whereX1is one‐dimension, X(2)isp2‐ dimensional, and so 1 +p1+p2=p.Let ρ1and ρ be the multiple correlation coefficients ofX1withX(2)and with (X'(2),X'(3))', respectively. Write ρ2/2 = ρ2‐ ρ2/1. We shall cosider the fol