
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22010.59    174.6207    22955.16    21668.31    22352.86
experime |  17,281    21637.66    171.6106    22559.45    21301.28    21974.03
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            372.9308    244.8318               -106.9475    852.8091
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    diff = mean(control) - mean(experime)                         t =   1.5232
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9361         Pr(|T| > |t|) = 0.1277          Pr(T > t) = 0.0639
