
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21665.82    172.9136    22730.74    21326.89    22004.75
experime |  17,281    21982.42    173.3338    22785.98    21642.67    22322.18
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -316.6065    244.8341               -796.4893    163.2763
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    diff = mean(control) - mean(experime)                         t =  -1.2931
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0980         Pr(|T| > |t|) = 0.1960          Pr(T > t) = 0.9020
