calc_q3: calc_q3 ***********************************************************
Description
#q3 is about the fraction missing F1 scores. If that is larger than NA.threshold, q3=0;
else q3 depends on the fraction scored F1's
Usage
calc_q3(F1.NAfrac, fracNA_threshold)
Arguments
F1.NAfrac
Fraction of missing values in the F1
fracNA_threshold
Threshold for fraction missing values