The life of p: "Just significant" results are on the rise

Nathan Leggett, Nicole Thomas, Tobias Loetscher, Michael Nicholls

    Research output: Contribution to journalArticlepeer-review

    39 Citations (Scopus)

    Abstract

    Null hypothesis significance testing uses the seemingly arbitrary probability of.05 as a means of objectively determining whether a tested effect is reliable. Within recent psychological articles, research has found an overrepresentation of p values around this cut-off. The present study examined whether this overrepresentation is a product of recent pressure to publish or whether it has existed throughout psychological research. Articles published in 1965 and 2005 from two prominent psychology journals were examined. Like previous research, the frequency of p values at and just below.05 was greater than expected compared to p frequencies in other ranges. While this overrepresentation was found for values published in both 1965 and 2005, it was much greater in 2005. Additionally, p values close to but over.05 were more likely to be rounded down to, or incorrectly reported as, significant in 2005 than in 1965. Modern statistical software and an increased pressure to publish may explain this pattern. The problem may be alleviated by reduced reliance on p values and increased reporting of confidence intervals and effect sizes.

    Original languageEnglish
    Pages (from-to)2303-2309
    Number of pages7
    JournalQuarterly Journal of Experimental Psychology
    Volume66
    Issue number12
    DOIs
    Publication statusPublished - 2013

    Keywords

    • Hypothesis testing
    • p value
    • Publication
    • Statistical inference
    • Statistics

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