How can we compute the error or uncertainty in measuring an operator O ?
It is stupid, because it's first of all poorly worded and then wrongly formulated. As i said above, we measure obervables, but we can't compute the errors, nor the any uncertainty. We can compute some statistical quantities, like mean square deviation, dispersion, mean, probability of an outcome, etc.This is definately a very stupid exam question.
I just thought that there is some mathematical formula or that ΔO (uncertainty) is related somehow to Werner Heisenberg's uncertainty principle.