How confidence intervals become confusion intervals

BMC Med Res Methodol. 2013 Oct 31:13:134. doi: 10.1186/1471-2288-13-134.


Background: Controversies are common in medicine. Some arise when the conclusions of research publications directly contradict each other, creating uncertainty for frontline clinicians.

Discussion: In this paper, we review how researchers can look at very similar data yet have completely different conclusions based purely on an over-reliance of statistical significance and an unclear understanding of confidence intervals. The dogmatic adherence to statistical significant thresholds can lead authors to write dichotomized absolute conclusions while ignoring the broader interpretations of very consistent findings. We describe three examples of controversy around the potential benefit of a medication, a comparison between new medications, and a medication with a potential harm. The examples include the highest levels of evidence, both meta-analyses and randomized controlled trials. We will show how in each case the confidence intervals and point estimates were very similar. The only identifiable differences to account for the contrasting conclusions arise from the serendipitous finding of confidence intervals that either marginally cross or just fail to cross the line of statistical significance.

Summary: These opposing conclusions are false disagreements that create unnecessary clinical uncertainty. We provide helpful recommendations in approaching conflicting conclusions when they are associated with remarkably similar results.

MeSH terms

  • Anticoagulants / therapeutic use
  • Benzazepines / adverse effects
  • Benzazepines / therapeutic use
  • Cardiovascular Diseases / drug therapy
  • Cardiovascular Diseases / etiology
  • Cardiovascular Diseases / mortality
  • Confidence Intervals
  • Data Interpretation, Statistical*
  • Evidence-Based Medicine
  • Humans
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors / therapeutic use
  • Quinoxalines / adverse effects
  • Quinoxalines / therapeutic use
  • Randomized Controlled Trials as Topic
  • Risk
  • Treatment Outcome
  • Uncertainty
  • Varenicline


  • Anticoagulants
  • Benzazepines
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors
  • Quinoxalines
  • Varenicline