
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21883.22    173.9534    22867.43    21542.25    22224.19
experime |  17,281    21765.02    172.2975    22649.76     21427.3    22102.74
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            118.1982    244.8392               -361.6946     598.091
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    diff = mean(control) - mean(experime)                         t =   0.4828
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6854         Pr(|T| > |t|) = 0.6293          Pr(T > t) = 0.3146
