
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21823.35    174.8292    22982.56    21480.66    22166.03
experime |  17,281    21824.89      171.41    22533.08    21488.91    22160.88
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -1.546774      244.84               -481.4412    478.3476
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    diff = mean(control) - mean(experime)                         t =  -0.0063
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4975         Pr(|T| > |t|) = 0.9950          Pr(T > t) = 0.5025
