
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21606.9    172.7847    22713.79    21268.23    21945.58
experime |  17,281    22041.34    173.4549     22801.9    21701.35    22381.33
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -434.4335    244.8289               -914.3061    45.43902
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    diff = mean(control) - mean(experime)                         t =  -1.7744
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0380         Pr(|T| > |t|) = 0.0760          Pr(T > t) = 0.9620
