
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21987.23    176.8174    23243.93    21640.65    22333.81
experime |  17,281    21661.01    169.3492    22262.17    21329.07    21992.95
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            326.2173    244.8337               -153.6648    806.0994
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    diff = mean(control) - mean(experime)                         t =   1.3324
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9086         Pr(|T| > |t|) = 0.1827          Pr(T > t) = 0.0914
