
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21927.93    173.9733    22870.05    21586.92    22268.93
experime |  17,281    21720.32    172.2749    22646.79    21382.64    22057.99
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            207.6112    244.8375               -272.2782    687.5007
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    diff = mean(control) - mean(experime)                         t =   0.8480
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8018         Pr(|T| > |t|) = 0.3965          Pr(T > t) = 0.1982
