
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21918.86    173.8738    22856.96    21578.05    22259.67
experime |  17,281    21729.38     172.376    22660.07     21391.5    22067.25
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            189.4836    244.8379               -290.4067    669.3738
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    diff = mean(control) - mean(experime)                         t =   0.7739
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7805         Pr(|T| > |t|) = 0.4390          Pr(T > t) = 0.2195
