
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21880.71    173.2755    22778.31    21541.07    22220.35
experime |  17,281    21767.53    172.9794    22739.39    21428.48    22106.59
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            113.1751    244.8392               -366.7178     593.068
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    diff = mean(control) - mean(experime)                         t =   0.4622
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6780         Pr(|T| > |t|) = 0.6439          Pr(T > t) = 0.3220
