
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21900.82    172.1728    22633.36    21563.34    22238.29
experime |  17,281    21747.42    174.0761    22883.56    21406.22    22088.63
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            153.3955    244.8386               -326.4962    633.2872
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    diff = mean(control) - mean(experime)                         t =   0.6265
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7345         Pr(|T| > |t|) = 0.5310          Pr(T > t) = 0.2655
