
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21692.05    171.9756    22607.43    21354.96    22029.14
experime |  17,281    21956.19     174.267    22908.66    21614.61    22297.77
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -264.1403    244.8359               -744.0266    215.7461
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    diff = mean(control) - mean(experime)                         t =  -1.0788
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1403         Pr(|T| > |t|) = 0.2807          Pr(T > t) = 0.8 597
