
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21924.99    173.8133    22849.01     21584.3    22265.68
experime |  17,281    21723.25    172.4366    22668.04    21385.26    22061.25
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            201.7348    244.8376               -278.1549    681.6245
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    diff = mean(control) - mean(experime)                         t =   0.8240
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7950         Pr(|T| > |t|) = 0.4100          Pr(T > t) = 0.2050
