
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21761.98    171.5622    22553.09     21425.7    22098.26
experime |  17,281    21886.26    174.6785    22962.75    21543.87    22228.65
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -124.282    244.8391               -604.1746    355.6106
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    diff = mean(control) - mean(experime)                         t =  -0.5076
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3059         Pr(|T| > |t|) = 0.6117          Pr(T > t) = 0.6941
