Data on the modulus of elasticity obtained 1 minute after loading in a certain configuration and 4 weeks after loading for the same lumber specimens is presented here.

Observation 1 min 4 weeks Difference
1 10,659 9,253 1406
2 16,620 13,250 3370
3 17,300 14,720 2580
4 15,557 12,240 3317
5 12,970 10,120 2850
6 17,260 14,570 2690
7 13,400 11,220 2180
8 13,149 11,649 1500
9 13,630 11,420 2210
10 13,260 10,910 2350
11 14,370 12,110 2260
12 11,230 8,040 3190
13 15,470 12,590 2880
14 17,840 15,090 2750
15 14,070 10,550 3520
16 14,303 12,458 1845

Calculate and interpret an upper confidence bound for the true average difference between 1-minute modulus and 4-week modulus; first check the plausibility of any necessary assumptions. (Use ? = 0.05. Round your answer to the nearest whole number.)

a) Upper Confidence Bound: ?