ARIMA MODEL OF OUTLIER DETECTION FOR FORECASTING CONSUMER PRICE INDEX (CPI)

Abstract

The Consumer Price Index (CPI) is an indicator used by Badan Pusat Statistik (BPS) which describes the average change in the prices paid by urban consumers for a market basket of consumer goods and services in a certain period. In the case of the CPI of Probolinggo City, if the CPI increases then describe inflation occurs and conversely. The CPI of Probolinggo City increase is not fixed. This study is to forecast the Consumer Price Index (CPI) and the result can be used as one of the considerations in carrying out economic development in the future. The research focused on the data of the CPI of Probolinggo City from January 2014 to April 2022. The methodology implemented in this study is Autoregressive Integrated Moving Average (ARIMA). The result shows that ARIMA (0,2,1) without an outlier was the best model for predicting the CPI of Probolinggo City for the next 8 months. This model shows the value of MAPE is 1.69%. The value of forecasting results in each month has decreased and increased not so significantly where in May 2022 the forecasting value was 108,391 then in June 2022 the forecasting value became 108,411 and so on until December 2022 the forecasting results using ARIMA model (0,2,1) of 107,845.