
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21843.77    174.1984    22899.63    21502.33    22185.22
experime |  17,281    21804.47    172.0509    22617.33    21467.23    22141.71
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            39.30565    244.8399               -440.5886    519.1999
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    diff = mean(control) - mean(experime)                         t =   0.1605
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5638         Pr(|T| > |t|) = 0.8725          Pr(T > t) = 0.4 362
