Example: At the time of writing, a special promotion gives you a voucher to save $75 USD on an exam when you buy an approved certification study book.

例如，在撰写本文时，IBM 举办的 特价促销活动 会发放一些优惠券，只要您购买某本权威认证书籍，就可以为考试节省 $75 美元。

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Still, a larger study of a privately-funded voucher scheme in New York in which the recipients are chosen by lot showed similar levels of improvement.

ECONOMIST: Sorting out school choice

Harvard's study of the Milwaukee schools found that, after four years, pupils in voucher schools had maths scores 11 percentage points higher than their unlucky public contemporaries, and six points higher in reading.

ECONOMIST: Sorting out school choice