
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21885.54     174.256    22907.21    21543.98     22227.1
experime |  17,281     21762.7    171.9914    22609.51    21425.58    22099.82
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             122.841    244.8391               -357.0517    602.7336
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    diff = mean(control) - mean(experime)                         t =   0.5017
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6921         Pr(|T| > |t|) = 0.6159          Pr(T > t) = 0.3079
