
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21883.26    174.4171    22928.39    21541.38    22225.13
experime |  17,281    21764.98    171.8281    22588.04    21428.18    22101.78
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            118.2773    244.8392               -361.6155    598.1701
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    diff = mean(control) - mean(experime)                         t =   0.4831
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6855         Pr(|T| > |t|) = 0.6290          Pr(T > t) = 0.3145
