
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21884.91     173.975    22870.26     21543.9    22225.92
experime |  17,281    21763.33    172.2757    22646.88    21425.65    22101.01
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            121.5829    244.8391               -358.3098    601.4756
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    diff = mean(control) - mean(experime)                         t =   0.4966
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6903         Pr(|T| > |t|) = 0.6195          Pr(T > t) = 0.3097
