
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21860.81     174.295    22912.33    21519.17    22202.44
experime |  17,281    21787.44    171.9527    22604.43    21450.39    22124.48
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            73.36902    244.8397               -406.5248    553.2628
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    diff = mean(control) - mean(experime)                         t =   0.2997
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6178         Pr(|T| > |t|) = 0.7644          Pr(T > t) = 0.3822
