
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21956.69    173.6728    22830.55    21616.27     22297.1
experime |  17,281    21691.56    172.5756    22686.31    21353.29    22029.82
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            265.1309    244.8359               -214.7553    745.0172
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    diff = mean(control) - mean(experime)                         t =   1.0829
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8606         Pr(|T| > |t|) = 0.2789          Pr(T > t) = 0.1394
