Analisis variasi length of stay los dan biaya perawatan pasien Jaminan Kesehatan Nasional (JKN) : studi kasus pada 5 (lima) Casemix Main Group (CMG) di RSUP Fatmawati tahun 2015 - 2017 = Analysis of length of stay and cost variation in Jaminan Kesehatan Nasional (JKN) patients case study in 5 ffve Casemix Main Groups in Fatmawati General Hospital in 2015-2017