What possible sources of bias might have been introduced into the study by using this method of sampling.

由于使用该样本收集方法，该项研究有可能存在的偏见来源有哪些？

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In communications and transportation circumstances survey, the method of sampling survey was used regularly.

在交通运输情况调查中，经常采用抽样调查的方法。

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In this paper, the problem about information value is proposed, evaluation method of sampling information value is given.

本文提出了信息价值的问题，并给出了抽样信息价值的评价方法。

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However, the researchers said that despite a lower number of invasive tests, the heavier reliance of this method on chorionic villus sampling earlier in pregnancy could actually mean an increase in the number of healthy babies lost if the miscarriage rate using this method was closer to 2%.

BBC: Down's test miscarriage warning

Because the 1990 Census undercounted millions of Americans, mostly minorities, the Clinton administration proposed the sampling method as a way of ensuring a more accurate count in 2000.

ECONOMIST: Sampling is wrong: official

This concern, however, is being allayed with the advent of techniques such as Dr Song's mobile-sampling method.

ECONOMIST: The biology of business