The fraction of reads deemed informative over the entire cohort
INFO=<ID=FractionInformativeReads,Number=1,Type=Float,Description="The fraction of informative reads out of the total reads">
The FractionInformativeReads annotation produces a single fraction for each site: sum(AD)/sum(DP). The sum in the numerator is over all the samples in the cohort and all the alleles in each sample. The sum in the denominator is over all the samples.