"Obs"	"Y"	"X1"	"X2"
1	4	0	0
2	4	0	0
3	4	0	0
4	6	0	0
5	6	0	0
6	6	0	0
7	11	0	1
8	13	0	1
9	6	1	0
10	8	1	0
11	13	1	1
12	13	1	1
13	13	1	1
14	15	1	1
15	15	1	1
16	15	1	1