
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.                                             [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21863.31      173.84    22852.52                                              21522.57                                              22204.06
experime |  17,281    21784.93    172.4126    22664.88                                              21446.98                                              22122.88
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6                                              21584.18                                              22064.06
---------+--------------------------------------------------------------------
    diff |            78.38313    244.8396               -401.5106                                              558.2768
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    diff = mean(control) - mean(experime)                         t =   0.3201
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6256         Pr(|T| > |t|) =  0.7489          Pr(T > t) = 0.3744
