This note revisits Maity and Sherman’s two-sample testing problem
with one variance known but the other one unknown [A. Maity,
M. Sherman, The two-sample t test with one variance unknown,
The American Statistician 60 (2006) 163–166]. Inspired by the fact
that the number of degrees of freedom used in their testing method
is overestimated, we propose in this note a new testing method
by introducing an unbiased estimator of the number of degrees
of freedom. Simulation studies indicate that the proposed testing
method provides a more accurate control than Maity and Sherman’s
method.