Fisher A A, Carlaw R W
Stud Fam Plann. 1983 Jan;14(1):3-8.
This report discusses the experience of a two-year family planning and maternal/child health project in Nepal. Although the project was planned as an experimental field research endeavor, a series of unanticipated events repeatedly compromised the internal validity of the project and forced design changes. While unexpected events are common in the history of most field projects, they present the research evaluator with the fundamental dilemma of trying to maintain a high degree of internal validity without sacrificing external validity. Rigid research designs with tight control over the introduction and measurement of experimental variables may serve to increase internal validity but they may also create an atypical and artificial situation that fails to mirror real field conditions and thus threatens external validity.
本报告讨论了尼泊尔一个为期两年的计划生育与母婴健康项目的经验。尽管该项目原本计划作为一项实验性实地研究工作，但一系列意外事件屡屡损害了项目的内部效度，并迫使进行设计变更。虽然意外事件在大多数实地项目的历史中很常见，但它们给研究评估者带来了一个基本困境，即试图在不牺牲外部效度的情况下保持高度的内部效度。对实验变量的引入和测量进行严格控制的严格研究设计可能有助于提高内部效度，但也可能创造出一种非典型的、人为的情况，无法反映真实的实地条件，从而威胁到外部效度。
