Seasonal Analysis of Transformations of the Multiplicative Time Series Model

Transformations of the purely multiplicative time series model will either remain the purely multiplicative model or the additive time series model. These transformations are required to meet the variant assumptions on either the multiplicative or the additive models with respect to the seasonal component. When these assumptions are met, a transformation is regarded as being successful with respect to the seasonal component. This study deals with the methods required in the determination of intervals for the seasonal indices for successful transformations. Intervals derived are found to lie in the neighbourhood of 1.0. Numerical examples are used to illustrate the results obtained.