
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21903.49    176.2241    23165.93    21558.07     22248.9
experime |  17,281    21744.76    169.9735    22344.24    21411.59    22077.92
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            158.7288    244.8385               -321.1627    638.6203
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    diff = mean(control) - mean(experime)                         t =   0.6483
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7416         Pr(|T| > |t|) = 0.5168          Pr(T > t) = 0.2 584
