The bond prices question is a pretty bad filter, since it doesn't give the competent candidate much chance to express how they think, and a weak candidate has a good chance of guessing "they go down" and even a fair chance of blustering their way through followup questions/explanations.
On the flip side, you could probably unintentionally trip up someone with a generally competent grasp of economics/stats but a lack of specific interest in bonds over terminology if your followup questions start asking them to distinguish between types of yield.
Same with exchange rates (although I do remember back in school in a competitive presentation being complemented on my confident and plausible sounding explanation of the effect of an interest rate rise on exchange rates that also happened to be the reverse of the correct answer :-) )
On the flip side, you could probably unintentionally trip up someone with a generally competent grasp of economics/stats but a lack of specific interest in bonds over terminology if your followup questions start asking them to distinguish between types of yield.
Same with exchange rates (although I do remember back in school in a competitive presentation being complemented on my confident and plausible sounding explanation of the effect of an interest rate rise on exchange rates that also happened to be the reverse of the correct answer :-) )