NIST is another statistical method counting n-gram co-ocurrence based on BLEU, which assigns a higher weight to a more informative n-gram co-ocurrence with a less number occurring in references.

NIST在BLEU方法的基础上，提出了另外一种基于共现n元词的统计方法，它认为如果一个n元词在参考译文中出现的次数越少，那么该n元词包含的信息量就越大，就应该赋予更高的权重。

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