
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21890.12     173.517    22810.06    21550.01    22230.23
experime |  17,281    21758.12    172.7367    22707.49    21419.54     22096.7
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            131.9983     244.839                -347.894    611.8907
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    diff = mean(control) - mean(experime)                         t =   0.5391
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7051         Pr(|T| > |t|) = 0.5898          Pr(T > t) = 0.2949
