
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21873.5    173.2788    22778.75    21533.85    22213.14
experime |  17,281    21774.75    172.9763    22738.99    21435.69     22113.8
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            98.75143    244.8394               -381.1418    578.6447
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    diff = mean(control) - mean(experime)                         t =   0.4033
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6566         Pr(|T| > |t|) = 0.6867          Pr(T > t) = 0.3434
