Table 1. Multiplet frequencies for three hypothetical experiments in which human and mouse cells are mixed equally.

Experiment	Human droplets	Mouse droplets	Non-empty droplets	Human and mouse droplets	Multiplet freq	Twice cross celltype freq
1	2,005	2,005	4,000	10	0.005	0.005
2	2,050	2,050	4,000	100	0.049	0.050
3	2,500	2,500	4,000	1,000	0.425	0.500

Notes:

The multiplet frequencies calculated using the exact method described here (column multiplet freq) are very similar to those obtained simply by multiplying by two the fraction of non-empty droplets that contain cells of both types (column twice cross celltype freq). However, the two methods are slightly different at higher multiplet frequencies, since the latter method fails to account for multiplets that have more than two cells.