
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22036.17    175.0259    23008.42     21693.1    22379.24
experime |  17,281    21612.07    171.1939    22504.68    21276.52    21947.63
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            424.0964    244.8294               -55.77715      903.97
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    diff = mean(control) - mean(experime)                         t =   1.7322
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9584         Pr(|T| > |t|) = 0.0832          Pr(T > t) = 0.0416
