
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21861.25     173.304    22782.06    21521.56    22200.95
experime |  17,281    21786.99    172.9515    22735.72    21447.99    22125.99
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            74.26402    244.8397               -405.6297    554.1578
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    diff = mean(control) - mean(experime)                         t =   0.3033
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6192         Pr(|T| > |t|) = 0.7617          Pr(T > t) = 0.3808
