
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21557.66    169.6366    22299.95    21225.15    21890.16
experime |  17,281    22090.58    176.5272    23205.77    21744.57    22436.59
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -532.925    244.8232               -1012.786   -53.06348
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    diff = mean(control) - mean(experime)                         t =  -2.1768
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0148         Pr(|T| > |t|) = 0.0295          Pr(T > t) = 0.9852
