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1 April 2010 Invasive Plant Researchers Should Calculate Effect Sizes, Not P-Values
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Null hypothesis significance testing (NHST) forms the backbone of statistical inference in invasive plant science. Over 95% of research articles in Invasive Plant Science and Management report NHST results such as P-values or statistics closely related to P-values such as least significant differences. Unfortunately, NHST results are less informative than their ubiquity implies. P-values are hard to interpret and are regularly misinterpreted. Also, P-values do not provide estimates of the magnitudes and uncertainties of studied effects, and these effect size estimates are what invasive plant scientists care about most. In this paper, we reanalyze four datasets (two of our own and two of our colleagues; studies put forth as examples in this paper are used with permission of their authors) to illustrate limitations of NHST. The re-analyses are used to build a case for confidence intervals as preferable alternatives to P-values. Confidence intervals indicate effect sizes, and compared to P-values, confidence intervals provide more complete, intuitively appealing information on what data do/do not indicate.

Matthew J. Rinella and Jeremy J. James "Invasive Plant Researchers Should Calculate Effect Sizes, Not P-Values," Invasive Plant Science and Management 3(2), 106-112, (1 April 2010).
Received: 27 May 2009; Accepted: 1 January 2010; Published: 1 April 2010

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