
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22089.58    175.5282    23074.45    21745.53    22433.63
experime |  17,281    21558.66    170.6702    22435.83    21224.13    21893.19
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            530.9156    244.8233                51.05383    1010.777
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    diff = mean(control) - mean(experime)                         t =   2.1686
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9849         Pr(|T| > |t|) = 0.0301          Pr(T > t) = 0.0151
