题目
In regard to modeling and forecasting seasonality, each of the following is true EXCEPT which is not accurate?
选项
A.A seasonal time series is, by definition, covariance stationary
B.Trading-day variation is a type of seasonality that refers to the fact that different months contain different numbers of trading days
C.A key technique for modeling seasonality is regression on seasonal dummy variables; dummy variables assume a value of zero or one.
D.Log transformation is useful in both trend models and seasonal models, but for different reasons; in a seasonal model, log transformation can stabilize seasonal patterns whose variance is growing over time
答案
A
解析
A seasonal time series is not covariance stationary.季节性的时间序列不是协方差平稳。