Sampling strategy has critical implications for the validity of a researcher's conclusions. Despite this, sampling is frequently neglected in research methods textbooks, during the research design process, and in the reporting of our journals. The lack of guidance on this issue often leads reviewers and journal editors to rely on simple rules of thumb, myth, and tradition for judgments about sampling, which promotes the unnecessary and counterproductive characterization of sampling strategies as universally "good" or "bad." Such oversimplification, especially by journal editors and reviewers, slows the progress of the social sciences by considering legitimate data sources to be categorically unacceptable. Instead, we argue that sampling is better understood in methodological terms of range restriction and omitted variables bias. This considered approach has far-reaching implications because in industrialorganizational (I-O) psychology, as in most social sciences, virtually all of the samples are convenience samples. Organizational samples are not gold standard research sources; instead, they are merely a specific type of convenience sample with their own positive and negative implications for validity. This fact does not condemn the science of I-O psychology but does highlight the need for more careful consideration of how and when a finding may generalize based on the particular mix of validityrelated affordances provided by each sample source that might be used to investigate a particular research question. We call for researchers to explore such considerations cautiously and explicitly both in the publication and in the review of research.Despite its importance, external validity receives only cursory treatment in most research methods textbooks. Even handbooks are light on coverage; in their lengthy, classic reference work on research methods, Pedhazur 142 a r b i t r a ry di st i nc t ion s be t w e e n c on v e n i e nc e s a m pl e s 143 and Schmelkin (1991) devoted a scant four of their 819 pages to external validity, whereas Shadish, Cook, and Campbell (2002) provided a comparatively rigorous treatment with approximately 10 pages. In part because internal validity is a prerequisite for external validity, much greater focus in these volumes is placed on internal validity and the various techniques to maximize it. This bias is reflected more broadly in the writing and review process as well; although authors will devote pages of text to measure identification, experimental design, and analytic strategy, considerations related to external validity are often limited to a token paragraph in a limitations section. Given this focus in both seminal texts and current research literature, we suspect the balance of coverage in graduate education is similarly skewed.With such a lack of guidance, many journal reviewers are left to rely on their own idiosyncratic reasoning as to whether external validity is threatened in a particular study. The use of obvious convenience sampling, in particular, is a lightning rod for...

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Background and Aim Gamification has been defined as the use of characteristics commonly associated with video games in non-game contexts. In this article, I reframe this definition in terms of the game attribute taxonomy presented by Bedwell and colleagues. This linking is done with the goal of aligning the research literatures of serious games and gamification. A psychological theory of gamified learning is developed and explored. Conclusion In the theory of gamified learning, gamification is defined as the use of game attributes, as defined by the Bedwell taxonomy, outside the context of a game with the purpose of affecting learning-related behaviors or attitudes. These behaviors/attitudes, in turn, influence learning by one or two processes: by strengthening the relationship between instructional design quality and outcomes (a moderating process) and/or by influencing learning directly (a mediating process). This is contrasted with a serious games approach in which manipulation of game attributes is typically intended to affect learning without this type of behavioral mediator/moderator. Examples of each game attribute category as it might be applied in gamification are provided, along with specific recommendations for the rigorous, scientific study of gamification.

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