When Testing for Differences of Means, the T-Statistic T = $\frac { \bar { Y } m - \bar { Y } w } { S E ( \bar { Y } m - \overline { \bar { Y } w } ) }$

When testing for differences of means, the t-statistic t = $\frac { \bar { Y } m - \bar { Y } w } { S E ( \bar { Y } m - \overline { \bar { Y } w } ) }$ , where $S E \left[ \bar { Y } _ { m } - \bar { Y } _ { W } \right) = \sqrt { \frac { s _ { m } ^ { 2 } } { n _ { m } } + \frac { s _ { w } ^ { 2 } } { n _ { w } } }$ has

A) a student t distribution if the population distribution of Y is not normal
B) a student t distribution if the population distribution of Y is normal
C) a normal distribution even in small samples
D) cannot be computed unless $n _ { w }$ = $n _ { m }$