
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21737.27    172.4149    22665.19    21399.32    22075.22
experime |  17,281    21910.97    173.8357    22851.96    21570.23    22251.71
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -173.6984    244.8382               -653.5893    306.1926
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    diff = mean(control) - mean(experime)                         t =  -0.7094
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.2390         Pr(|T| > |t|) = 0.4781          Pr(T > t) = 0.7610
