
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21855.61    172.7086    22703.79    21517.08    22194.14
experime |  17,281    21792.63    173.5462    22813.89    21452.46     22132.8
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            62.97957    244.8398               -416.9144    542.8735
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    diff = mean(control) - mean(experime)                         t =   0.2572
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6015         Pr(|T| > |t|) = 0.7970          Pr(T > t) = 0.3985
