
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21659.82    170.6199    22429.22    21325.39    21994.25
experime |  17,281    21988.42    175.5914    23082.76    21644.24     22332.6
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -328.599    244.8336               -808.4809    151.2829
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    diff = mean(control) - mean(experime)                         t =  -1.3421
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0898         Pr(|T| > |t|) = 0.1796          Pr(T > t) = 0.9102
