
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21876.08    174.3756    22922.93    21534.29    22217.87
experime |  17,281    21772.16    171.8705    22593.62    21435.28    22109.05
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            103.9161    244.8394                -375.977    583.8093
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    diff = mean(control) - mean(experime)                         t =   0.4244
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6644         Pr(|T| > |t|) = 0.6713          Pr(T > t) = 0.3356
