While meaningful comparisons can be made between the NCS values of reference signatures with respect to query q, it is also useful to assess if the connectivity between q and a particular signature r is significantly different from that observed between r and other queries. This is done by comparing each observed NCS value ncsq,r between the query q and a reference signature r to a distribution of NCS values representing the similarities between a reference compendium of queries (Qref) and r. This procedure results in a standardized measure we refer to as Tau (τ) that ranges from -100 to +100 and represents the percentage of queries in Qref with a lower |NCS| than |ncsq,r|, adjusted to retain the sign of ncsq,r:
