
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21822.49    173.1733    22764.88    21483.05    22161.93
experime |  17,281    21825.75    173.0827    22752.98    21486.49    22165.01
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -3.260818      244.84               -483.1552    476.6336
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    diff = mean(control) - mean(experime)                         t =  -0.0133
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4947         Pr(|T| > |t|) = 0.9894          Pr(T > t) = 0.5053
