
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21789.88    172.7598    22710.53    21451.25    22128.51
experime |  17,281    21858.36    173.4951    22807.18    21518.29    22198.43
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -68.47849    244.8397               -548.3723    411.4154
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    diff = mean(control) - mean(experime)                         t =  -0.2797
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3899         Pr(|T| > |t|) = 0.7797          Pr(T > t) = 0.6101
