
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21941.42    176.1541    23156.72    21596.14    22286.69
experime |  17,281    21706.83    170.0435    22353.44    21373.52    22040.13
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            234.5883    244.8368               -245.2997    714.4764
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   0.9581
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8310         Pr(|T| > |t|) = 0.3380          Pr(T > t) = 0.1690
