
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21950.49    175.0754    23014.93    21607.33    22293.66
experime |  17,281    21697.75    171.1531    22499.31    21362.27    22033.23
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            252.7465    244.8362               -227.1405    732.6335
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    diff = mean(control) - mean(experime)                         t =   1.0323
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8490         Pr(|T| > |t|) = 0.3019          Pr(T > t) = 0.1510
