THE TRANSFORMATION OF LOCAL LESION COUNTS FOR STATISTICAL ANALYSIS
- 1 March 1949
- journal article
- research article
- Published by Wiley in Annals of Applied Biology
- Vol. 36 (1) , 139-152
- https://doi.org/10.1111/j.1744-7348.1949.tb06404.x
Abstract
An analysis of the frequency distribution of local lesions, produced by viruses on half‐leaves of a number of plants, shows that their standard error increases with increasing mean. Hence analysis of variance and statistical tests of significance should not be applied to lesion numbers unless they are suitably transformed. The transformation into logarithms over‐corrects so that the standard error decreases with increasing mean. A satisfactory transformation is y= log10 (x+c), where x is the number of lesions and c is a constant. A method is given of assessing c for different experiments. Great accuracy is not needed; in an experiment discussed in detail a satisfactory transformation is obtained with any value for c between 15 and 80.On individual plants the numbers of lesions formed on half‐leaves are distributed more or less normally, whereas their distribution about the common mean for many plants is skew and ‘leptokurtic’. The distribution of the transformed numbers is almost normal, both for individual plants and about the common mean for a number of plants.Keywords
This publication has 2 references indexed in Scilit:
- The moments of the distribution for normal samples of measures of departure from normalityProceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, 1930
- Local Lesions in Tobacco MosaicBotanical Gazette, 1929