
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21631.56    171.7332    22575.56    21294.95    21968.18
experime |  17,281    22016.68    174.4994    22939.21    21674.64    22358.72
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -385.1151    244.8312               -864.9923     94.7621
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    diff = mean(control) - mean(experime)                         t =  -1.5730
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0579         Pr(|T| > |t|) = 0.1157          Pr(T > t) = 0.9421
