
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21878.28    172.3053    22650.78    21540.54    22216.02
experime |  17,281    21769.96    173.9459    22866.44    21429.01    22110.91
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            108.3183    244.8393               -371.5748    588.2113
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    diff = mean(control) - mean(experime)                         t =   0.4424
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6709         Pr(|T| > |t|) = 0.6582          Pr(T > t) = 0.3291
