
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21685.32    171.7436    22576.93    21348.68    22021.95
experime |  17,281    21962.93    174.4951    22938.64     21620.9    22304.95
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -277.6113    244.8355               -757.4968    202.2742
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    diff = mean(control) - mean(experime)                         t =  -1.1339
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1284         Pr(|T| > |t|) = 0.2569          Pr(T > t) = 0.8716
