名词
中文翻译：前后测试
同义词：
['before-and-after study', 'before-and-after experiment', 'before-and-after comparison test']
例句：
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1. This is a before-and-after test of the new policy.
这是对新政策的前后对比测试。
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2. The teacher conducted a before-and-after test to see how much students improved.
老师进行了前后对比测试，看看学生有多大的进步。
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3. Before-and-after tests are often used in scientific research to compare results from different experiments.
在科学研究中，前后对比测试常用于比较不同实验的结果。