A comparative evaluation framework of instructional interventions for implementation of online training for public library staff would enable a better understanding of how to improve the effectiveness, efficiency and efficacy of training in certain training environments. This dissertation describes a quasi-experimental study of a two-week, asynchronous online training course that was provided at four levels of instructional intervention to public library staff in the United States. The course content addressed the complex issues of difficult patron policy development and situational coping techniques. The objective of the study was to develop and demonstrate a theoretically grounded, evidence-based impact evaluation framework. The framework was used to assess the relative impact of an online course for public librarians at four levels of instructional intervention. The researcher investigated the relationships between the type of e-Training instructional interventions and the short- and long-term impacts on participants' knowledge, self-efficacy, and workplace performance. The study used a longitudinal, quasi-experimental design that included a pretest, posttest and three-month delayed posttest with follow-up survey. 194 participants completed all three phases of the study. The evaluation tools measured course content related knowledge and self-efficacy at all three phases (pretest, posttest, and delayed posttest) and assessed workplace application of training at 3-month follow-up. The results of this study contributed to evaluation theory and learning theory literature applied to the online learning environment and informed public library staff online training practices and evaluation methodologies.