
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21571.49    170.0217    22350.58    21238.23    21904.75
experime |  17,281    22076.75    176.1586    23157.32    21731.46    22422.04
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -505.2559    244.8249               -985.1208   -25.39112
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    diff = mean(control) - mean(experime)                         t =  -2.0637
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0195         Pr(|T| > |t|) = 0.0390          Pr(T > t) = 0.9805
