Sample correlation matrix
= Sample correlation matrix
{title2=$R_{jk}=S_{jk}/\sqrt{S_{jj}S_{kk}}$}
A <sample correlation matrix> rescales a <sample covariance matrix> $S$ to unit diagonal, for variables with positive sample variance. Its off-diagonal entries are <sample correlation coefficients>. Strong correlations between predictors can indicate <multicollinearity>, but pairwise correlations alone do not exclude higher-order linear dependence.