
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21798.73    175.7084    23098.14    21454.32    22143.13
experime |  17,281    21849.51    170.5084    22414.56     21515.3    22183.73
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -50.78712    244.8399               -530.6812     429.107
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    diff = mean(control) - mean(experime)                         t =  -0.2074
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4178         Pr(|T| > |t|) = 0.8357          Pr(T > t) = 0.5822
