这是一篇基于次级资料的概念性论文。
调研人员开始调查时总是先收集次级资料以判断问题是否部分或全部解决了，而不是先去收集成本很高的初级资料。
Researchers usually start their investigation by examining secondary data to see whether their problem can be partly or wholly solved without collecting costly primary data.
我们在主要与关键次级结果中，以随机效应模式将资料进行统合分析，并正式地评估其异质性。
We meta-analysed data using a random-effects model on the primary and key secondary outcomes and formally assessed heterogeneity.
我们在主要与关键次级结果中，以随机效应模式将资料进行统合分析，并正式地评估其异质性。
We meta-analysed data using a random-effects model on the primary and key secondary outcomes and formally assessed heterogeneity.
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