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我们梳理了GRE写作的Argument任务中常见的逻辑漏洞类型。这一讲开始，我们逐个击破。我们首先来看一下“【分母】问题“。
题目中给出的passage里有这么一句话：“… Another study, however, suggests that during the same ten-year period, the number of accidents caused by bicycling has increased 200 percent. …”。 这句话就出现了“不讨论分母的分子都是耍流氓”，也就是典型的“【分母】问题”。我们首先回忆一下“【分母】问题”的模型，如下： 1、关键词：百分比形式的表述。 2、逻辑：分子的数字越大，数字本身越大。 3、诊断：缺失分母或者错误的分母会造成数字大的错觉。
接下来，我们看一下老师的分析和写作示范：
Although it is known that there has been a 200-percent increase in the number of accidents caused by bicycling, what remains a question is about the total number of bicyclists and the number ten years ago. If there have been more bicyclists on the road, the chance of having accidents has actually decreased although the number of accidents has increased. For example, 10 accidents out of 1000 bicyclists represents a lower percentage than 5 accidents out of 200 bicyclists.
我们再看一个例子：
题目给出的passage中有一句话说到：“… During the past year, Quiot Manufacturing had 30 percent more on-the-job accidents than at the nearby Panoply Industries plant…” 符合我们总结出的“【分母】问题”的模型： 1、关键词：百分比形式的表述。 2、逻辑：分子的数字越大，数字本身越大。 3、诊断：缺失分母或者错误的分母会造成数字大的错觉。 A crucial yet deceptive assumption is that the two plants have the same scale of production—the number of production activities or products. At this point, the author confuses the number of accidents with the incidence of accidents. In fact, Quiot may have a lower rate of accidents despite its 30 percent more accidents. For example, 13 accidents out of 1000 production activities equals an accident rate of 1.3%, and this rate would be lower than Panoply’s if there are 10 accidents out of 500 production activities at Panoply.
首先，通过以上两个例子，大家可以理解“【分母】问题”的形式。同时，大家也可以总结出针对“【分母】问题”的分析和写作套路。
其次，有同学可能发现（尤其是在第二个例子中）：“【分母】问题”可能与“【混淆/偷换概念】问题”有极大的重叠，甚至是同一种问题的两种不同的理解角度。
那么，是否需要区分？如果需要区分，如何区分？
我们在下一讲会击破“【混淆/偷换概念】问题”，并且帮助大家理解这两类问题的异同。