The study sounds simple, but the design of the experiments was actually somewhat complex, because the researchers had to overcome a number of confounding variables.

这个实验听起来很简单，但是实验的设计确实有一定程度的复杂性，因为研究人员不得不克服一些混淆变量。

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They also knew that, by working with surveys from three countries, and with such a wide range of ages, they would diversify the data and iron out confounding variables.

他们也明白研究三个国家的调查结果，而且是这么广的年龄跨度，他们能使数据多样化且消除混杂变量。

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Internal validity: the degree to which the results of a study can be attributed to the treatment rather than extraneous or confounding variables.

内部效度：一个实验结果归咎于实验处理，而非归咎于无关的混淆的变量的程度。

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There are many confounding variables, however, that affect the value of a business aircraft, and without considerable research it can be difficult to pinpoint the best aircraft for you.

FORBES: What's The Best Jet For You? (Part 3)