
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21840.2    173.5959    22820.44    21499.94    22180.47
experime |  17,281    21808.04    172.6588    22697.24    21469.61    22146.47
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            32.15934    244.8399               -447.7349    512.0536
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    diff = mean(control) - mean(experime)                         t =   0.1313
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5522         Pr(|T| > |t|) = 0.8955          Pr(T > t) = 0.4478
