You are tasked with forecasting the next monthly sales value…
You are tasked with forecasting the next monthly sales value using an ARIMA(3,1,2) model based on the following information: The last 4 months of actual sales data (in units) are: 300, 320, 315, and 330. The errors (residuals) from the previous two months’ forecasts are 5 and -7, respectively. The ARIMA(3,1,2) model has the following parameters: ϕ1=0.6 ϕ2=0.3 ϕ3=−0.2 θ1=0.8 θ2=0.5 Assume there is no constant (μ=0) in the model. Using this information, calculate the forecast for the next month.