Dielectric and dynamic mechanical measurements were carried out on poly(vinylethylene) in the vicinity of its glass transition temperature. By using four different spectrometers, data were obtained over a broad range of frequencies and temperatures. The shape of the segmental relaxation function, though weakly temperature dependent, was the same for the two experimental probes when compared at the same temperature. Similarly, the shift factors, describing the temperature dependence of the segmental relaxation time, were equivalent as measured dielectrically or mechanically. Such equivalence is consistent with a correlation between time and temperature dependencies of the segmental relaxation; moreover, it demonstrates that the correlation is maintained even when different dynamical variables (e.g., dipole moment versus modulus) are used to probe the local segmental motion. In contrast to the shape of the relaxation function and the time-temperature shift factors, the correlation times measured by the two spectroscopies bear no relationship to one another.