
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21910.52    175.1899    23029.97    21567.13    22253.91
experime |  17,281    21737.72    171.0388    22484.29    21402.47    22072.98
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            172.7972    244.8382               -307.0938    652.6881
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    diff = mean(control) - mean(experime)                         t =   0.7058
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7598         Pr(|T| > |t|) = 0.4803          Pr(T > t) = 0.2402
