
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21630.13    169.3239    22258.85    21298.24    21962.02
experime |  17,281    22018.11     176.838    23246.63    21671.49    22364.73
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -387.9803    244.8311               -867.8573    91.89665
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    diff = mean(control) - mean(experime)                         t =  -1.5847
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0565         Pr(|T| > |t|) = 0.1130          Pr(T > t) = 0.9435
