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Learning Objectives

After completing this chapter, the reader will be able to:

  • Identify skills health care practitioners need to evaluate medical literature and apply it to patient care.

  • Describe special characteristics of a controlled clinical trial that distinguish this research design as the prototype for clinical research.

  • Prepare a null hypothesis (H0) based upon the clinical trial objective(s) and endpoint(s).

  • Differentiate between the types of data, measures of central tendency, and measures of variability.

  • Differentiate between Type I and Type II errors; discuss methods to reduce the possibility of either of these errors occurring.

  • Interpret p values and 95% confidence interval (CI); discuss whether to reject or fail-to-reject the H0 by using these clinical trial results.

  • Calculate and interpret relative risk (RR), relative risk reduction (RRR), absolute risk reduction (ARR), and number needed to treat (NNT).

  • State whether statistical significance and clinical difference are present using the clinical trial results.

  • Explain the purpose and usage of editorials, letters to the editor, and secondary journals in critiquing clinical trials and the application of results into practice.

  • Identify key features of adaptive clinical trials and noninferiority trials.


Key Concepts

  • image Practitioners need to be able to efficiently locate, critically analyze, and effectively communicate data from the primary literature to patients, other health care professionals, and the public.

  • image A controlled clinical trial is the gold-standard study design to measure and quantify effect differences between an intervention and a control.

  • image The entire published study should be read and thoroughly evaluated; decision-making should not rely solely on reading abstracts.

  • image The results of a controlled clinical trial should be extrapolated to the type of patient enrolled in the study, and readers should be aware of the limitations of surrogate endpoints and subgroup analyses.

  • image Randomization is an essential component of all controlled clinical trials that significantly differentiates them from other study designs.

  • image The controlled clinical trial primary endpoint should be appropriate for the study purpose and measured using valid techniques and methods.

  • image An appropriate sample size in a controlled clinical trial is vital for the study results to have any significant meaning; conducting a power analysis is important to determine a suitable sample size.

  • image Correctly interpreting p values is crucial to evaluating a controlled clinical trial; not all statistically significant p values are clinically important. The magnitude of difference in effect between the intervention and control cannot be determined with the p value.

  • image The use of 95% CI can assist the reader in assessing the magnitude of difference in effect between the intervention and control.

  • image Calculating measures of association (RR, ARR, RRR, NNT) for nominal data provides further information to interpret controlled clinical trial results

  • image Nonstatistically significant results do not equate to the intervention and control being the same or equal.

  • image All controlled clinical trial results need to be assessed to determine the clinical relevance of the intervention versus control.

  • image Controlled clinical trial investigators and ...

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