
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21703.92    172.9671    22737.77    21364.89    22042.96
experime |  17,281    21944.32     173.284    22779.43    21604.67    22283.97
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -240.3967    244.8366               -720.2844     239.491
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =  -0.9819
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1631         Pr(|T| > |t|) = 0.3262          Pr(T > t) = 0.8369
