
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21908.82    172.6403    22694.82    21570.43    22247.21
experime |  17,281    21739.42     173.612    22822.55    21399.12    22079.72
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            169.4001    244.8383                -310.491    649.2912
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   0.6919
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7555         Pr(|T| > |t|) = 0.4890          Pr(T > t) = 0.2445
