
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21847.12    172.2878    22648.48    21509.42    22184.82
experime |  17,281    21801.12     173.964    22868.82    21460.14    22142.11
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            45.99368    244.8399               -433.9005    525.8878
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    diff = mean(control) - mean(experime)                         t =   0.1879
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5745         Pr(|T| > |t|) = 0.8510          Pr(T > t) = 0.4255
