
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21911.06    175.1769    23028.27    21567.69    22254.42
experime |  17,281    21737.19    171.0521    22486.03    21401.91    22072.47
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            173.8687    244.8382               -306.0222    653.7596
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    diff = mean(control) - mean(experime)                         t =   0.7101
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7612         Pr(|T| > |t|) = 0.4776          Pr(T > t) = 0.2388
