
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21817.42    173.8268    22850.78     21476.7    22158.13
experime |  17,281    21830.83    172.4264     22666.7    21492.85     22168.8
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -13.41003      244.84               -493.3044    466.4843
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    diff = mean(control) - mean(experime)                         t =  -0.0548
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4782         Pr(|T| > |t|) = 0.9563          Pr(T > t) = 0.5218
