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455 24 ADVANTAGES OF CERTAINTY AND UNCERTAINTY WENDY WOOD ALICE H. EAGLY Duke University Northwestern University C O N T E N T S 24.1 Introduction 456 24.2 Estimating Relations Between Variables 457 24.2.1 Implications of Relations Held with Certainty 459 24.2.2 Uncertainty Attributable to Unexplained Heterogeneity 459 24.2.3 Uncertainty Attributable to Lack of Generalizability 460 24.3 Evaluating Moderators and Mediators of an Effect 462 24.3.1 Moderators of Main-Effect Findings 462 24.3.2 Strategies Given Moderators of Low Certainty 463 24.3.3 Mediators of Main-Effect Findings 465 24.3.4 Strategies Given Low Certainty About Mediators 467 24.4 Using Main Effects, Moderators, and Mediators to Test Theories Competitively 467 24.4.1 Mechanisms of Competitive Theory Testing 468 24.4.2 Strategies Given Low Certainty About Competing Theories 469 24.5 Uncertain and Certain Findings Direct Subsequent Research 469 24.6 Conclusion 470 24.7 References 471 456 TYING RESEARCH SYNTHESIS TO SUBSTANTIVE ISSUES 24.1 INTRODUCTION A research synthesis typically is not an endpoint in the investigation of a topic. Rarely does a synthesis offer a definitive answer to the theoretical or empirical question that inspired the investigation. Instead, most research syntheses serve as way stations along a sometimes winding research path. The goal is to describe the status of a research literature by highlighting what is unknown as well as what is known. It is the unknowns that are especially likely to suggest useful directions for new research. The purpose of this chapter is to delineate the possible relations between research syntheses, theory development , and future empirical research. By indicating the weaknesses as well as the strengths of existing research, a synthesis can channel thinking about research and theory in directions that would improve the next generation of empirical evidence and theoretical development. In general, scientists’belief about what the next steps are for empirical research and theorizing following a synthesis depends on the level of certainty that they accord its findings (see Cooper and Rosenthal 1980). In this context, certainty refers to the confidence with which the scientific community accepts empirical associations between variables and the theoretical explanations for these associations . As we explain in this chapter, the certainty accorded to findings is influenced by the perceived validity of the research . In a meta-analysis, invalidity can arise at the level of the underlying studies as well as at the meta-analytic, aggregate level. Threats to validity, as William Shadish, Thomas Cook, and Donald Campbell defined it, reduce scientists’ certainty about the empirical relations and theoretical explanations considered in a meta-analysis, and this uncertainty in turn stimulates additional research (2002). Empirical relations and theoretical explanations in research syntheses range from those that the scientific community can accept with high certainty to those it can hold with little certainty only. Highly certain conclusions suggest that additional research of the kind evaluated is not required to substantiate the focal effect or validate the theoretical explanation, whereas less certain conclusions suggest a need for additional research. Our proposal to evaluate the uncertainty that remains in empirical relations and in interpretations of those relations challenges more standard ways of valuing research findings. Generally, evaluation of research, be it by journal editors or other interested scientists, favors valid empirical findings and well-substantiated theories. In this conventional approach, science progresses through the cumulation of well-supported findings and theories. Although it is standard practice for researchers to call for additional investigation at the end of a written report, such requests are often treated as rhetorical devices that have limited meaning in themselves. In our experience, editors’ publication decisions and manuscript reviewers’ evaluations are rarely influenced by such indicators of sources of uncertainty that could be addressed in future investigation. Following scientific convention, research syntheses would be evaluated favorably to the extent that they produce findings and theoretical statements that appear to contribute definitively to the canon of scientific knowledge . In striving to meet such criteria, the authors of syntheses might focus on what is known in preference to what is unknown. In contrast, we believe that, by highlighting points of invalidity in a research literature, research syntheses offer an alternative, generative route for scientific progress. This generative route does not produce valid findings and theoretical statements but instead identifies points of uncertainty and thus promising avenues for subsequent research and theorizing that can reduce the uncertainty . When giving weight to the generative contribution of a...

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