
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21765.31    172.0269    22614.18    21428.12     22102.5
experime |  17,281    21882.93     174.221    22902.61    21541.44    22224.42
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -117.6225    244.8392               -597.5153    362.2703
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    diff = mean(control) - mean(experime)                         t =  -0.4804
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3155         Pr(|T| > |t|) = 0.6309          Pr(T > t) = 0.6845
