
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21905.63    174.1898    22898.51     21564.2    22247.06
experime |  17,281    21742.61    172.0574    22618.19    21405.36    22079.86
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            163.0232    244.8384               -316.8682    642.9145
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    diff = mean(control) - mean(experime)                         t =   0.6658
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7472         Pr(|T| > |t|) = 0.5055          Pr(T > t) = 0.2528
