
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21863.02    173.1868    22766.65    21523.56    22202.48
experime |  17,281    21785.22    173.0688    22751.14    21445.99    22124.45
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            77.79995    244.8396               -402.0937    557.6937
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    diff = mean(control) - mean(experime)                         t =   0.3178
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6247         Pr(|T| > |t|) = 0.7507          Pr(T > t) = 0.3753
