
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21856.39    174.2922    22911.97    21514.76    22198.03
experime |  17,281    21791.85    171.9556    22604.81     21454.8     22128.9
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            64.54738    244.8398               -415.3465    544.4413
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    diff = mean(control) - mean(experime)                         t =   0.2636
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6040         Pr(|T| > |t|) = 0.7921          Pr(T > t) = 0.3960
