ABSTRACT
Objective To study the function of X -1 2 -ARIMA model in analysis on incidence trend of typhoid. Methods Secular trend,seasonal periodicity and random fluctuations of the monthly morbidity data in Zhejiang province from 2005 to 201 3 were analyzed by X -1 2 -ARIMA model.Results The seasonal fluctuation showed a narrowing trend year by year during 2005 to 201 3.After September,2007,the incidence of typhoid showed a downward trend.After 2008,the annual peak of incidence changed from August to July.The irregular factor may well represent the outbreak. Conclusion The X -1 2 -ARIMA model showed clear secular trend and seasonal periodicity,and the random fluctuation was of great value.
ABSTRACT
Objective To study the methods of the Chinese New Year (CNY) Factor's Adjustment based on the ARIMA models. Methods First, a common regressor for CNY was created. Then, the re-gressor was included in the seasonal ARIMA regressive model(regARIMA or TRAMO) ,AIC or BIC was used for model selection,and the generalized least squares method or maximum likelihood method was used for the earl-mation of model parameter. The estimated regressive coefficient was used for analyzing the degree of the CNY factor. A case was analyzed with the adjustment methods. Results The analysis on the case showed that the methods of the CNY factor's adjustment could remove the effects of the CNY factor on the time series, and the degree of the effects could be esti-mated in quantity. Conclusion The regressor for CNY is applicable,and the methods of the CNY factor's adjustment based on the ARIMA models can be used in seasonal adjustment on the time series. It's a new approach to analyze the effects of the CNY factor.