
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21733.62    170.9664    22474.77    21398.51    22068.73
experime |  17,281    21914.62    175.2603    23039.23    21571.09    22258.15
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -180.9999    244.8381               -660.8905    298.8907
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    diff = mean(control) - mean(experime)                         t =  -0.7393
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.2299         Pr(|T| > |t|) = 0.4598          Pr(T > t) = 0.7701
