However, the study lacked a control group and used nonrandom sampling, they noted.

然而，这项研究缺乏一个控制组并且采用的是非随机抽样，他们表示。

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Methods: Nonrandom purposive sampling was used to select key respondents to conduct indepth interview.

方法：采用非随机、目的抽样方法选择被访者，对关键知情人进行个人深入访谈。

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