title: The spectre of 'spurious' correlations.
abstract: Ecologists often 'standardize' data through the use of ratios and indices. Such measures are employed generally to remove a 'size effect' induced by some relatively uniteresting variable. The implications of using the resultant data in correlation and regression analyses are poorly recognized. We show that ratios and indices often provide surprising and 'spurious' results due to their unusual properties. As a solution, we advocate the use of randomization tests to evaluate hypotheses confounded by 'spurious' correlations. In addition, we emphasize that identifying the appropriate null correlation is of utmost importance when statistically evaluating ratios, although this issue is frequently ignored.
authors.affiliation: Department of Zoology, University of Toronto, M5S 1A1, Toronto, Ontario, Canada.
authors.forename: D A
authors.initials: DA
authors.lastname: Jackson
authors.affiliation: Department of Zoology, University of Toronto, M5S 1A1, Toronto, Ontario, Canada.
authors.forename: K M
authors.initials: KM
authors.lastname: Somers
keywords: Data standardization; Randomization tests; Ratios; Spurious correlation; Statistical inference