
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21764.98    172.2294     22640.8    21427.39    22102.57
experime |  17,281    21883.26    174.0208     22876.3    21542.16    22224.36
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -118.2792    244.8392                -598.172    361.6135
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =  -0.4831
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3145         Pr(|T| > |t|) = 0.6290          Pr(T > t) = 0.6855
