On Semiparametric Testing of I(d) by FEXP Models

To statistically test the assumption that a scalar-valued process is I(d), this article proposes a test statistic based on a broadband semiparametric method by use of fractional exponential (FEXP) models. The test is semiparametric in terms of flexibility in modeling spectral density. We establish the asymptotic behavior and report finite-sample performance by a Monte Carlo study.