Thirty-eight percent of the Nature papers and a quarter of the BMJ articles studied contained at least one statistical error, according to Emili Garca-Berthou, a lecturer on biostatistics at University of Girona, Spain, and Carles Alcaraz. In total, more than 11% of the statistical results published in the two journals during 2001 were incongruent.
"Our findings confirm that the quality of research and scientific papers needs improvement and should be more carefully checked and evaluated in these days of high publication pressure," write the authors.
The errors seen could have been caused by transcription or typesetting errors, for example if a repeated zero was omitted. Alternatively, researchers may have rounded up figures incorrectly.
The researchers showed that some numbers, four and nine, were seen less often than would be expected at the end of a given test statistic or P-value, suggesting that researchers were rounding up numbers incorrectly, possibly so that they looked 'neater'. For example study authors might round up 2.38 to 2.5 rather than 2.4.
"Although these kinds of errors may leave the conclusions of a study unchanged, they are indicative of poor practice," say the researchers. "Our concern is that these kinds of errors are probably present in all numerical results and all steps of scientific research, with potentially important practical consequences."
The researchers suggest that one way to minimise the effect of these errors would be for published authors to make the
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BioMed Central
27-May-2004