
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22113.32    175.2679    23040.24    21769.78    22456.87
experime |  17,281    21534.92     170.933    22470.38    21199.87    21869.96
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            578.4041    244.8202                98.54845     1058.26
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    diff = mean(control) - mean(experime)                         t =   2.3626
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9909         Pr(|T| > |t|) = 0.0182          Pr(T > t) = 0.0091
