
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21915.76    175.1273    23021.75    21572.49    22259.03
experime |  17,281    21732.48    171.1026    22492.67     21397.1    22067.86
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             183.278     244.838               -296.6125    663.1685
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    diff = mean(control) - mean(experime)                         t =   0.7486
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7729         Pr(|T| > |t|) = 0.4541          Pr(T > t) = 0.2271
