
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21493.38    170.3634     22395.5    21159.45     21827.3
experime |  17,281    22154.87    175.8132    23111.92    21810.25    22499.48
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -661.4915    244.8141               -1141.335   -181.6478
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    diff = mean(control) - mean(experime)                         t =  -2.7020
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0034         Pr(|T| > |t|) = 0.0069          Pr(T > t) = 0.9966
