
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21699.58    170.3858    22398.44    21365.61    22033.56
experime |  17,281    21948.66    175.8224    23113.13    21604.03    22293.29
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -249.0726    244.8363               -728.9598    230.8146
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    diff = mean(control) - mean(experime)                         t =  -1.0173
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1545         Pr(|T| > |t|) = 0.3090          Pr(T > t) = 0.8455
