
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21973.23    174.5303    22943.27    21631.13    22315.33
experime |  17,281    21675.01    171.7068     22572.1    21338.45    22011.57
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            298.2197    244.8347               -181.6644    778.1038
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    diff = mean(control) - mean(experime)                         t =   1.2180
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8884         Pr(|T| > |t|) = 0.2232          Pr(T > t) = 0.1116
