
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22006.76    175.3637    23052.83    21663.03    22350.49
experime |  17,281    21641.48    170.8518     22459.7     21306.6    21976.37
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            365.2751    244.8321               -114.6038     845.154
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    diff = mean(control) - mean(experime)                         t =   1.4919
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9321         Pr(|T| > |t|) = 0.1357          Pr(T > t) = 0.0679
