sing an additive time series model, the quarterly trend (Y) is given by Y = 65 + 7t, where t is the quarter (starting with t = 1 in the first quarter of 20X5). If the seasonal component in the fourth quarter is -30, what is the forecast for the actual value for the fourth quarter of 20X6, to the nearest whole number?
A、63
B、546
C、85
D、91
A、63
B、546
C、85
D、91
【参考答案及解析】
If t = 1 in the first quarter of 20X5 t = 8 in the fourth quarter of 20X6 Trend (Y) = 65 + (7 x 8)=121 Forecast = trend + seasonal component =121 + (-30)=121 - 30 =91
If t = 1 in the first quarter of 20X5 t = 8 in the fourth quarter of 20X6 Trend (Y) = 65 + (7 x 8)=121 Forecast = trend + seasonal component =121 + (-30)=121 - 30 =91