
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21863.26    175.4197    23060.18    21519.42     22207.1
experime |  17,281    21784.99    170.8051    22453.57    21450.19    22119.78
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            78.27086    244.8396               -401.6228    558.1646
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    diff = mean(control) - mean(experime)                         t =   0.3197
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6254         Pr(|T| > |t|) = 0.7492          Pr(T > t) = 0.3746
