
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21902.28    175.4714    23066.98    21558.34    22246.22
experime |  17,281    21745.96    170.7505    22446.38    21411.27    22080.65
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            156.3182    244.8386               -323.5734    636.2098
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    diff = mean(control) - mean(experime)                         t =   0.6385
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7384         Pr(|T| > |t|) = 0.5232          Pr(T > t) = 0.2616
