Trials with ‘non-significant’ results are not insignificant trials: a common significance threshold distorts reporting and interpretation of trial results

Abstract

We discuss a newly published study examining how phrases are used in clinical trials to describe results when the estimated P-value is close to (slightly above or slightly below) 0.05, which has been arbitrarily designated by convention as the boundary for ‘statistical significance’. Terms such as ‘marginally significant’, ‘trending towards significant’, and ‘nominally significant’ are well represented in biomedical literature, but are not actually scientifically meaningful. Acknowledging that ‘statistical significance’ remains a major determinant of publication, we propose that scientific journals de-emphasise the use of P-values for null hypothesis significance testing, a purpose for which they were never intended, and avoid the use of these ambiguous and confusing terms in scientific articles. Instead, investigators could simply report their findings: effect sizes, P-values, and confidence intervals (or their Bayesian equivalents), and leave it to the discerning reader to infer the clinical applicability and importance. Our goal should be to move away from describing studies (or trials) as positive or negative based on an arbitrary P-value threshold, and rather to judge whether the scientific evidence provided is informative or uninformative.