Unfortunately, the findings of confirmatory trials are often misinterpreted. There is no guarantee that a hypothesis is true just because it passes a statistically significant test. The significance level, typically 5%, represents the likelihood of a false positive result. Hence, systematic reviews and meta-analyses, which lessen the uncertainty by integrating the findings from multiple trials of the same endpoint, play a significant role in the pursuit of truth.
Conversely, confirmatory trials that fail to confirm the tested hypothesis because of statistical nonsignificance are frequently presented to the reader as negative trials. See, for example, Que et al. (1) "this was a negative trial as it failed to reach its primary endpoint."
However, a negative trial offers evidence that the intervention does not have any significant impact on the outcome under investigation, and statistical nonsignificance is not such evidence. There are several other reasons why a statistically significant effect might not be present, such as a too small sample size. Showing that a drug's effect is comparable to that of a placebo, requires a successful equivalence trial, not a failed superiority trial. If it cannot be determined in an unsuccessful trial whether the intervention is beneficial, neutral, or harmful, it is inconclusive.
References
1. Que LG, Yang Z, Lugogo NL, Katial RK, Shoemaker SA, Troha JM, Rodman DM, Tighe RM, Kraft M. Effect of the S-nitrosoglutathione reductase inhibitor N6022 on bronchial hyperreactivity in asthma. Immun Inflamm Dis. 2018 Jun;6(2):322-331. doi: 10.1002/iid3.220. Epub 2018 Apr 11. PMID: 29642282; PMCID: PMC5946144.
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