
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22092.33    175.7045    23097.62    21747.93    22436.73
experime |  17,281    21555.91    170.4883    22411.91    21221.74    21890.09
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            536.4146     244.823                56.55355    1016.276
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    diff = mean(control) - mean(experime)                         t =   2.1910
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9858         Pr(|T| > |t|) = 0.0285          Pr(T > t) = 0.0142
