The following set of reading taken with a level: 1.565, 0.985, 1.235, 2.545, 3.455, 1.875, 1.985, 0.865 and 1.285. If the instrument was shifted after the 2nd and the 5th reading then the entries in the foresight column would be
1
0.985, 3.455 and 1.285
2
0.985, 1.875 and 1.285
3
1.235, 1.985 and 1.285
4
1.235, 1.985 and 0.865