
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21945.72    173.4536    22801.73    21605.73     22285.7
experime |  17,281    21702.52    172.7969     22715.4    21363.82    22041.22
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            243.1936    244.8365                -236.694    723.0811
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    diff = mean(control) - mean(experime)                         t =   0.9933
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8397         Pr(|T| > |t|) = 0.3206          Pr(T > t) = 0.1603
