
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21832.91    172.2668    22645.72    21495.25    22170.57
experime |  17,281    21815.34    173.9849    22871.57    21474.31    22156.36
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             17.5699      244.84               -462.3245    497.4643
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    diff = mean(control) - mean(experime)                         t =   0.0718
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5286         Pr(|T| > |t|) = 0.9428          Pr(T > t) = 0.4714
