Sherman M A, Rath G J, Schofer J L, Thompson C W
Med Care. 1979 Feb;17(2):127-38. doi: 10.1097/00005650-197902000-00003.
Much of the literature concerning emergency medical services evaluation has been criticized as unconvincing. Several sources of invalidity have comprised the interpretability of these studies. When true randomized experiments cannot be accomplished, quasi-experimental research designs offer greater interpretability than the more often used pre-experimental designs. In using quasi-experimental research designs, special attention must be given to threats to internal validity. A case study describes an evaluation of mobile intensive care units. The paper describes eighteen threats to the validity of the evaluation, as well as the methods used for their control. Whether or not evaluators can control all of the threats to the validity of their studies, these threats should be identified and their potential effects assessed wherever possible.
许多关于紧急医疗服务评估的文献都被批评为缺乏说服力。这些研究的可解释性存在几个无效性来源。当无法完成真正的随机实验时，准实验研究设计比更常用的预实验设计具有更高的可解释性。在使用准实验研究设计时，必须特别注意对内部效度的威胁。一个案例研究描述了对移动重症监护病房的评估。该论文描述了评估有效性的十八个威胁，以及用于控制这些威胁的方法。无论评估者是否能够控制其研究有效性的所有威胁，都应该识别这些威胁，并尽可能评估其潜在影响。
