你的书主要关注黑人中受过良好教育的“中产阶级”的婚姻模式。为什么把研究对象范围缩这么窄？
TIME:Your book focuses specifically on marriage patterns within the black "middle class" of educated professionals. Why focus your research so narrowly?
但因研究对象范围小以及研究对象的局限性，在有其他研究者进行此研究前，对此研究结果应持谨慎态度。
However, given the small sample size and limited nature of the population studied, naturally these results should be taken with a grain of salt until replicated by other researchers.
两名经济学家昨日分享了2009年诺贝尔经济学奖，他们的研究对象是，不在详细的合约或法律约束范围内的行为及交易。
Two economists who specialise in understanding behaviour and transactions which are not covered by detailed contracts or law shared the 2009 Nobel prize for economics yesterday.
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