The function computes the test statistics of the test proposed by Zhao, Duan, Zhao, and Sun (2013).
It is not to be called by the user.
Qiang Zhao and Jianguo Sun
X. Zhao, R. Duan, Q. Zhao, and J. Sun (2013), "A New Class of Generalized Log Rank Tests for Interval-censored Failure Time Data", Computational Statistics and Data Analysis. 60: 123-131.