Since the wire is vertical, the magnetic field produced by the wire should not be vertical, but horizontal. The vector you draw for Bv is vertical, I think that's why you're stuck.
Using the above formulas, we can arrive at an unbiased estimate of the standard deviation of the sample, then divide by sqrt(N) to arrive at the standard deviation of the average. What I'm confused about it where the measurement uncertainty comes into the equation. Is it being ignored? Say I...