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  • Print publication year: 2020
  • Online publication date: May 2020

Chapter 11 - Understanding P-Values and Confidence Intervals


In the previous two chapters, we discussed using the results of randomized trials and observational studies to estimate treatment effects. We were primarily interested in measures of effect size and in problems with design (in randomized trials) and confounding (in observational studies) that could bias effect estimates. We did not focus on whether the apparent treatment effects could be a result of chance or attempt to quantify the precision of our effect estimates. The statistics used to help us with these issues − P-values and confidence intervals – are the subject of this chapter.