  Joint ranking statistics are used to distinguish real from random
coincidences, ideally considering whether shared parameters are consistent with
each other as well as whether the individual candidates are distinguishable
from noise. We expand on previous works to include additional shared
parameters, we use galaxy catalogues aspriors for sky localization and
distance, and avoid some approximations previously used. We develop methods to
calculate this statistic both in low-latency using HEALPix sky maps, as well as
with posterior samples. We show that these changes lead to a factor of one to
two orders of magnitude improvement for GW170817-GRB 170817A depending on the
method used, placing this significant event further into the foreground. We
also examined the more tenuous joint candidate GBM-GW150914, which was largely
penalized by these methods. Finally, we performed a simplistic simulation that
argues these changes could better help distinguish between real and random
coincidences in searches, although more realistic simulations are needed to
confirm this.
