The exponential generalized autoregressive conditional heteroskedastic (EGARCH) model by Nelson (1991) is another form of the GARCH model.
where g(Z_{t})=\theta Z_{t}+\lambda(|Z_{t}. |-E(|Z_{t}|)), \sigma_{t}^{2} is the conditional variance, \omega, \beta, \alpha, \theta and \lambda are coefficients.