
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21903.09    173.0293    22745.95    21563.93    22242.24
experime |  17,281    21745.15    173.2246    22771.62    21405.62    22084.69
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            157.9322    244.8385               -321.9594    637.8237
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    diff = mean(control) - mean(experime)                         t =   0.6450
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7405         Pr(|T| > |t|) = 0.5189          Pr(T > t) = 0.2595
