
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22110.12    175.6272    23087.46    21765.88    22454.37
experime |  17,281    21538.12    170.5645    22421.93     21203.8    21872.44
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            572.0044    244.8207                92.14788    1051.861
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    diff = mean(control) - mean(experime)                         t =   2.3364
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9903         Pr(|T| > |t|) = 0.0195          Pr(T > t) = 0.0 097
