
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21886.54    172.6116    22691.04    21548.21    22224.88
experime |  17,281     21761.7    173.6416    22826.44    21421.34    22102.05
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            124.8455    244.8391               -355.0471    604.7381
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    diff = mean(control) - mean(experime)                         t =   0.5099
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6949         Pr(|T| > |t|) = 0.6101          Pr(T > t) = 0.3051
