Although biomedical statistics is part of any scientific curriculum, a review of the current scientific literature indicates that statistical data analysis is an area that frequently needs improvement. To address this, we here cover some of the most common problems in statistical analysis, with an emphasis on an intuitive, tutorial approach rather than a rigorous, proof-based one. The topics covered in this manuscript are whether to enter eyes or patients into the analysis, issues related to multiple testing, pitfalls surrounding the correlation coefficient (causation, insensitivity to patterns, range confounding, unsuitability for method comparisons), and when to use standard deviation (SD) versus standard error of the mean (SEM) “antennas” on graphs.
Correlation coefficient Independence Statistics Type I error Variability
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This work was supported by a grant from the Foundation Fighting Blindness, Columbia, Maryland and a grant from the Allene Reuss Memorial Trust, New York, New York.
Strasak AM, Zaman Q, Pfeiffer KP, Gobel G, Ulmer H (2007) Statistical errors in medical research—a review of common pitfalls. Swiss Med Wkly 137:44–49PubMedGoogle Scholar
Murdoch IE, Morris SS, Cousens SN (1998) People and eyes: statistical approaches in ophthalmology. Br J Ophthalmol 82:971–973CrossRefPubMedGoogle Scholar
Newcombe RG, Duff GR (1987) Eyes or patients? Traps for the unwary in the statistical analysis of ophthalmological studies. Br J Ophthalmol 71:645–646CrossRefPubMedGoogle Scholar
Rosner B (1984) Multivariate methods in opthalmology with application to other paired data situations. Biometrics 40:1025–1036CrossRefPubMedGoogle Scholar
Liang KY, Zeger SL (1986) Longitudinal data analysis using generalized linear models. Biometrika 73:13–22CrossRefGoogle Scholar
Katz J, Zeger S, Liang KY (1994) Appropriate statistical methods to account for similarities in binary outcomes between fellow eyes. Invest Ophthalmol Vis Sci 35:2461–2465PubMedGoogle Scholar
Glynn RJ, Rosner B (1992) Accounting for the correlation between fellow eyes in regression analysis. Arch Ophthalmol 110:381–387PubMedGoogle Scholar
Holm S (1979) A simple sequentially rejective multiple test procedure. Scand J Stat 6:65–70Google Scholar
Bland JM, Altman DG (1986) Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1:307–310PubMedGoogle Scholar
Cumming G, Finch S (2005) Inference by eye: confidence intervals and how to read pictures of data. Am Psychol 60:170–180CrossRefPubMedGoogle Scholar