Confounder selection is perhaps the most important step in the design of observational studies. A number of criteria, often with different objectives and approaches, have been proposed, and their validity and practical value have been debated in the literature. Here, we provide a unified review of these criteria and the assumptions behind them. We list several objectives that confounder selection methods aim to achieve and discuss the amount of structural knowledge required by different approaches. Finally, we discuss limitations of the existing approaches and implications for practitioners.

翻译：选择混乱者也许是设计观察研究的最重要步骤,提出了许多标准,往往有不同的目标和办法,并在文献中就这些标准的有效性和实用价值进行了辩论。在这里,我们统一审查这些标准及其背后的假设。我们列出了若干目标,这些选择方法混乱,目的是实现和讨论不同方法所需的结构知识的数量。最后,我们讨论了现有方法的局限性和对从业人员的影响。