
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22116.36    175.7842    23108.11    21771.81    22460.92
experime |  17,281    21531.88    170.4014     22400.5    21197.88    21865.88
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            584.4828    244.8198                 104.628    1064.338
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    diff = mean(control) - mean(experime)                         t =   2.3874
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9915         Pr(|T| > |t|) = 0.0170          Pr(T > t) = 0.0 085
