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INTRODUCTION

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Where Have You Been?

In Chapter 8, you learned about measures and the properties of measures. This included how these measures may inform your practice and to which measures you may give more attention. You also learned about several different types of research designs. You have learned about how experimental research is conducted and how a cause-and-effect relationship is implied. By extension, you have learned how clinical trials are types of experimental research extended to patient populations, and these trials include establishing both the efficacy and effectiveness of a treatment. You also learned about observational, epidemiological, and diagnostic trials. All these form the basis of how we understand the health and exercise sciences. The problem is that all these different types of research generate tremendous amounts of new information. Because of this, some mechanism of sorting all this information is needed.

Where Are You Going?

One way to sort through the large amount of new research being generated is for you as the practitioner to rely on reviews of the research. Reviews come in two basic forms: traditional narrative reviews and systematic reviews. Both can serve useful purposes. Narrative reviews are more prone to bias and may generate less accurate conclusions. Only the systematic review can establish whether a set of studies consistently supports the research hypothesis. The systematic review can also be extended to include a statistical analysis of the multiple study results. This is known as meta-analysis and is a very powerful tool for making sense of the existing literature.

Learning Outcomes

After reading this chapter, you should be able to answer these questions:

  1. What is the difference between a historical review and an expert review?

  2. How does bias affect the review process?

  3. What are the different types of bias?

  4. What are the solutions to bias?

  5. What is the difference between a systematic review and a meta-analysis?

  6. What is the advantage of a meta-analysis?

KEY TERMS

Key Terms

  • Bias

  • Citation bias

  • Duplication bias

  • Effect size

  • Expert review

  • Fail-safe N

  • Fixed effect model

  • Forest plot

  • Funnel plot

  • Historical review

  • Included study population

  • Language bias

  • Meta-analysis

  • Methodological quality

  • Narrative review

  • Overall effect size

  • Primary study

  • Publication bias

  • Random effects model

  • Raw mean difference

  • Secondary study

  • Sensitivity analysis

  • Standardized mean difference

  • Systematic review

  • Trim and fill

  • Vote counting

Research synthesis is the process of combining preexisting research studies into a single research study for understanding the larger meaning of the research. Research synthesis occurs in three basic forms: narrative reviews, systematic reviews, and an extension of systematic reviews called meta-analysis. To understand the synthesis process, narrative reviews are discussed first, followed by systematic reviews and meta-analysis. However, to understand these three, a distinction must first be made between two basic types of research literature.

PRIMARY STUDY VERSUS SECONDARY STUDY

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