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This excerpt was taken from line 1-2:
First, my attempt at translation: "In an international survey that was performed in 32 countries, in which one has made 15 year old children the target group, one has discovered that there was quite the difference depending on the country.”
What confuses me the most is 対象に. This に seems to me like the に in 音を大きくにします, where the subject changes the status of an object. The に expressing a decision could also work here, like in ビールにしますか、ビールにしますか。 In any case, the する after に isn't there in this case. So I don’t know for sure what function this に has.
What also makes me wonder is the では in 国際調査では. I’ve interpreted it as particle で + particle は. In a more literal translation, this still works: "Concerning in an international survey…., one has discovered….“ I just wonder why there is で at all. At least in the translation, it seems redundant.
Ultimately, I’d like to know whether my translation is precise. I usually hesitate making use of relative clauses, because one can easily scramble some relations without noticing. But since the attribute for 国際調査 was so complex, I didn’t see another way around it.