
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21833.19     171.546    22550.96    21496.94    22169.43
experime |  17,281    21815.06    174.6957    22965.01    21472.64    22157.48
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            18.12878      244.84               -461.7656    498.0231
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    diff = mean(control) - mean(experime)                         t =   0.0740
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5295         Pr(|T| > |t|) = 0.9410          Pr(T > t) = 0.4705
