
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21785.87    172.9627    22737.19    21446.85     22124.9
experime |  17,281    21862.37    173.2927    22780.58     21522.7    22202.04
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -76.49679    244.8397               -556.3905    403.3969
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    diff = mean(control) - mean(experime)                         t =  -0.3124
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3774         Pr(|T| > |t|) = 0.7547          Pr(T > t) = 0.6 226
