
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21787.87    172.6022     22689.8    21449.55    22126.19
experime |  17,281    21860.37    173.6518    22827.79       21520    22200.75
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -72.5068    244.8397               -552.4006     407.387
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    diff = mean(control) - mean(experime)                         t =  -0.2961
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3836         Pr(|T| > |t|) = 0.7671          Pr(T > t) = 0.6 164
