
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21866.56     173.481    22805.33    21526.52     22206.6
experime |  17,281    21781.68    172.7737    22712.35    21443.03    22120.33
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            84.88199    244.8396               -395.0116    564.7755
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    diff = mean(control) - mean(experime)                         t =   0.3467
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6356         Pr(|T| > |t|) = 0.7288          Pr(T > t) = 0.3644
