
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21906.13    173.7486     22840.5    21565.57    22246.69
experime |  17,281    21742.11     172.503    22676.77    21403.99    22080.24
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            164.0178    244.8384               -315.8734    643.9091
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    diff = mean(control) - mean(experime)                         t =   0.6699
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7485         Pr(|T| > |t|) = 0.5029          Pr(T > t) = 0.2515
