Studi pemanfaatan rawat jalan di Institusi Pelayanan Kabupaten Dharmasraya Dan Kota Sawahlunto Provinsi Sumatera Barat : analisis lanjut Data Susenas 2007 dan Riskesdas 2007 = The study of ambulatory care utilization in the Dharmasraya regency and Sawahlunto City West Sumatera province : continued analysis of Susenas data 2007 and Riskesdas data 2007