
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21890.76    173.8711    22856.62    21549.95    22231.56
experime |  17,281    21757.49    172.3802    22660.62     21419.6    22095.37
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            133.2688     244.839               -346.6235    613.1612
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    diff = mean(control) - mean(experime)                         t =   0.5443
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7069         Pr(|T| > |t|) = 0.5862          Pr(T > t) = 0.2931
