
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21791.62    172.7951    22715.17    21452.93    22130.32
experime |  17,281    21856.62    173.4599    22802.56    21516.62    22196.62
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -64.99308    244.8398                -544.887    414.9008
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    diff = mean(control) - mean(experime)                         t =  -0.2655
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3953         Pr(|T| > |t|) = 0.7907          Pr(T > t) = 0.6047
