
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21736.81    173.2077     22769.4     21397.3    22076.31
experime |  17,281    21911.44    173.0458    22748.12    21572.25    22250.62
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -174.6307    244.8382               -654.5215    305.2602
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    diff = mean(control) - mean(experime)                         t =  -0.7132
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.2378         Pr(|T| > |t|) = 0.4757          Pr(T > t) = 0.7622
