
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21670.87    173.0868    22753.51     21331.6    22010.14
experime |  17,281    21977.37    173.1614    22763.31    21637.96    22316.78
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -306.4998    244.8345               -786.3833    173.3837
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    diff = mean(control) - mean(experime)                         t =  -1.2519
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1053         Pr(|T| > |t|) = 0.2106          Pr(T > t) = 0.8947
