And I guess since they answer the questions at the bottom, it seems their intent is indeed the simplistic approach > The lower bound of which can be used to or

And I guess since they answer the questions at the bottom, it seems their intent is indeed the simplistic approach > The lower bound of which can be used to order the fractions, and so control the risk of over-estimation. It not clear to me from the question whether the cost of a mistake is in the over-estimating the underlying effect or in misranking the effects, and that seems like it would drive your heuristic selection.