
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21691.34    172.8155    22717.85     21352.6    22030.07
experime |  17,281    21956.91    173.4341    22799.16    21616.96    22296.85
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -265.5706    244.8358               -745.4568    214.3156
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    diff = mean(control) - mean(experime)                         t =  -1.0847
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1390         Pr(|T| > |t|) = 0.2781          Pr(T > t) = 0.8610
