
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22044.35    177.1057    23281.82     21697.2    22391.49
experime |  17,281    21603.89    169.0402    22221.55    21272.56    21935.23
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            440.4525    244.8285               -39.41948    920.3244
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    diff = mean(control) - mean(experime)                         t =   1.7990
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9640         Pr(|T| > |t|) = 0.0720          Pr(T > t) = 0.0360
