The life of p: “just significant” results are on the rise

Leggett, Nathan, Thomas, Nicole, Loetscher, Tobias, and Nicholls, Michael E.R. (2013) The life of p: “just significant” results are on the rise. Quarterly Journal of Experimental Psychology, 66 (12). pp. 2303-2309.

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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.

Item ID: 52458
Item Type: Article (Research - C1)
ISSN: 1747-0226
Keywords: statistics; statistical inference; hypothesis testing; p value; publication
Date Deposited: 03 May 2018 01:54
FoR Codes: 17 PSYCHOLOGY AND COGNITIVE SCIENCES > 1701 Psychology > 170110 Psychological Methodology, Design and Analysis @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970117 Expanding Knowledge in Psychology and Cognitive Sciences @ 100%
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