Drift Moves the Mean

Drift changes the mean position and leaves spread as a separate claim. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Drift speed 2 metres per second for 3 seconds gives mean position 6 metres.

2\cdot3=6

Diffusion is not the mean shift

The drift vector carries 6 metres; the spread claim is checked separately.

6\ \text{m mean shift}