Testing differences in relative growth rate: A method avoiding curve fitting and pairing |
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Authors: | Hendrik Poorter Charles Lewis |
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Affiliation: | Dept of Plant Physiology, Univ. of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands;Dept of Statistics and Measurement Theory (Social Sciences), Univ. of Groningen, Oude Boteringestraat 23, 9712 GC Groningen, The Netherlands. |
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Abstract: | A method is discussed to test differences in relative growth rates. This method is based on an analysis of variance, with In-transformed plant weight as dependent variable. A significant Group × Time interaction indicates differences in relative growth rates between groups. The advantages over the "classical" and "functional" growth analyses are: (1) No pairing procedure is required. (2) More than two groups may be evaluated in one analysis. (3) No decision is required about the polynomial used to fit the data. (4) By partitioning the interaction effect using orthogonal polynomials insight is gained into the nature of differences in relative growth rate. (5) By concentrating attention on the lower order terms of the polynomials, the influence of extraneous variation on conclusions may be minimized. |
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Keywords: | Growth analysis |
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