Replicate means are readable only after the spread gate is checked across rows. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The first replicate row passes inside the bound
Readings 10, 12, and 14 have mean 12 and half-range 2.
rˉ=12,h=2≤2
Equality at the spread limit still passes
Readings 12, 14, and 16 have half-range 2, exactly the limit 2.
rˉ=14,h=2≤2
A wider row fails before the mean is trusted
Readings 12, 16, and 20 still have a mean 16, but half-range 4 exceeds the limit.