
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21900.95    173.5462     22813.9    21560.78    22241.12
experime |  17,281    21747.29    172.7069    22703.56    21408.77    22085.81
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |              153.66    244.8386               -326.2316    633.5517
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    diff = mean(control) - mean(experime)                         t =   0.6276
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7349         Pr(|T| > |t|) = 0.5303          Pr(T > t) = 0.2651
