
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21898.87    174.6515     22959.2    21556.54     22241.2
experime |  17,281    21749.37    171.5891    22556.63    21413.04     22085.7
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            149.4982    244.8387               -330.3936      629.39
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    diff = mean(control) - mean(experime)                         t =   0.6106
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7293         Pr(|T| > |t|) = 0.5415          Pr(T > t) = 0.2707
