Generalization of an index of infection intensity in plant disease experiments

Abstract

In plant disease experiments, individuals of each experimental unit are commonly classified according to categories of a discrete quantitative scale through visual assessment of disease severity. This paper shows the generalization of a measure that associates a quantitative response called infection intensity index, expressed as I=sen²w, to each distribution of frequencies obtained in the units. Its angular transformation w=arcsen allows the application of the analysis of variance. Since the calculation of w does not involve the values or notes of the scale it can also be used with a qualitative ordinal scale.