
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21672.17    172.9212    22731.74    21333.23    22011.11
experime |  17,281    21976.07    173.3269    22785.07    21636.34    22315.81
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -303.9054    244.8345               -783.7891    175.9783
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    diff = mean(control) - mean(experime)                         t =  -1.2413
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1073         Pr(|T| > |t|) = 0.2145          Pr(T > t) = 0.8927
