来自《耶鲁大学开放课程：有关食物的心理学、生物学和政治学 第12集》

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  that's what we talked about before,
  这个我们之前讨论过
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  but you could do sequential cross-sectional studies
  但是你们也可以连续进行横向研究
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  and so some kind of tracking over time.
  也可以做些跟踪调查
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  But there are some weaknesses in this method as well,
  但是这个方法同样存在缺陷
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  but it's better than just having one snapshot in time of course.
  但比起一次性研究方法 这要好得多
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  This would be an example of a cross-sectional study,
  这个也是横向研究法的一个例子
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  but you're just taking different cross-sections over time.
  只是你是长时间进行横向研究法
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  Here would be an example of a cross-sectional study,
  再举个横向研究的例子
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  and I've showed you this graph before.
  这个图表你们之前看过了
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  This is the graph that shows body mass index,
  这个图上有身高体重指数
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  level of weight increasing on this axis,
  横轴表示体重上升水平
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  and then mortality rate on this axis,
  纵轴表示死亡率