
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21879.81    173.4843    22805.76    21539.76    22219.85
experime |  17,281    21768.43      172.77    22711.87    21429.79    22107.08
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            111.3739    244.8393               -368.5191    591.2669
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    diff = mean(control) - mean(experime)                         t =   0.4549
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6754         Pr(|T| > |t|) = 0.6492          Pr(T > t) = 0.3246
