其中 为白噪声过程
上述模型已经体现了ARCH模型的思想(也可以视为ARCH模型),但其以线性形式出现,不利于使用MLE同时对条件均值和条件异方差进行估计,此外,线性干扰项不如乘法干扰项易处理(引自Enders, W. (2014).Applied econometric time series(Fourth Edition). John Wiley & Sons. Page125)
因此Engle(1982)提出的ARCH(1)模型为
Tsay, R. S. (2005).Analysis of financial time series. John Wiley & Sons.
Wei, W. W. S. (1990).Time Series Univariate and Multivariate Methods. Pearson Addison Wesley.
Enders, W. (2008).Applied econometric time series. John Wiley & Sons.