The Partial Correlation coefficient with Information
Theory (PCIT) algorithm, combines the concept of
partial correlation coefficient with information theory to identify
significant gene-to-gene associations. For every trio of genes in $X_i$, $X_j$ and $X_l$, the three
first-order partial correlation
coefficients are computed. These coefficients
indicate the strength of the linear relationship between $X_i$ and
$X_j$ that is uncorrelated with $X_l$, being therefore a measure
of conditional independence. Then, the average ratio of partial to direct
correlation is computed in order to obtain the tolerance level to be used
as the local threshold for eliminating non-significant associations.