
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21870.33    172.9024    22729.27    21531.42    22209.23
experime |  17,281    21777.92    173.3527    22788.46    21438.13     22117.7
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            92.41061    244.8395               -387.4828     572.304
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    diff = mean(control) - mean(experime)                         t =   0.3774
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6471         Pr(|T| > |t|) = 0.7059          Pr(T > t) = 0.3529
