单一被试实验是特殊儿童心理与教育研究中的一种常用方法，但其外部效度往往受到质疑。
The single subject research is one of the useful methods in the research of special children's psychology and education, but its external validity often receives challenges.
本文是关于HSK外部效度的一次实证性研究。
This paper is an experimental study on the external validity of HSK.
控制具体测量过程中的无关变量的影响，保证统计处理的外部效度。
The researchers also should reduce the influence of irrelevant variables in measurement to guarantee the external validity of processing.
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