
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21978.26    175.3979    23057.32    21634.46    22322.06
experime |  17,281    21669.98      170.82    22455.52    21335.15     22004.8
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            308.2833    244.8344               -171.6001    788.1667
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    diff = mean(control) - mean(experime)                         t =   1.2592
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8960         Pr(|T| > |t|) = 0.2080          Pr(T > t) = 0.1040
