
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21869.33    174.2448    22905.73    21527.79    22210.87
experime |  17,281    21778.91    172.0033    22611.08    21441.77    22116.05
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            90.42011    244.8395               -389.4733    570.3136
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    diff = mean(control) - mean(experime)                         t =   0.3693
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6440         Pr(|T| > |t|) = 0.7119          Pr(T > t) = 0.3560
