
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21668.51    170.9171    22468.28     21333.5    22003.53
experime |  17,281    21979.73    175.3031    23044.86    21636.12    22323.34
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -311.2177    244.8343               -791.1008    168.6655
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    diff = mean(control) - mean(experime)                         t =  -1.2711
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1018         Pr(|T| > |t|) = 0.2037          Pr(T > t) = 0.8982
