
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21761.54    172.6988     22702.5    21423.04    22100.05
experime |  17,281     21886.7    173.5549    22815.04    21546.51    22226.88
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -125.1542    244.8391               -605.0468    354.7384
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    diff = mean(control) - mean(experime)                         t =  -0.5112
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3046         Pr(|T| > |t|) = 0.6092          Pr(T > t) = 0.6954
