
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21869.88    174.2599    22907.72    21528.31    22211.45
experime |  17,281    21778.36     171.988    22609.06    21441.25    22115.47
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            91.52049    244.8395               -388.3729    571.4139
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    diff = mean(control) - mean(experime)                         t =   0.3738
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6457         Pr(|T| > |t|) = 0.7086          Pr(T > t) = 0.3543
