The Certainty Behind Reporting a Significance Result: What the Clinician Should Know

The P value is the most common method used in medical literature for the result of a statistical test. It is the probability of the data with a true null hypothesis and is calculated using a formal statistical test after the appropriate model has been determined to analyze study data. The P value is dependent on the effect size, sample size, and a measure of variability within the outcomes. For many years, the P value has been set at 0.05, which is an arbitrary cutoff. It is important to understand that setting the cutoff at 0.05 may be correct for some study designs but not in others. Therefore, we recommend that in addition to the P value, another metric should be reported that specifies the magnitude of the effect such as effect size, confidence interval of the effect size, or fragility index.