
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21818.81    173.3998    22794.65    21478.93    22158.69
experime |  17,281    21829.44    172.8559    22723.15    21490.62    22168.25
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -10.62895      244.84               -490.5233    469.2654
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    diff = mean(control) - mean(experime)                         t =  -0.0434
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4827         Pr(|T| > |t|) = 0.9654          Pr(T > t) = 0.5173
