
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21738.98    173.4859    22805.98    21398.93    22079.03
experime |  17,281    21909.26    172.7669    22711.46    21570.62     22247.9
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -170.285    244.8383                -650.176    309.6061
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    diff = mean(control) - mean(experime)                         t =  -0.6955
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.2434         Pr(|T| > |t|) = 0.4867          Pr(T > t) = 0.7566
