
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21773.98    172.3345    22654.62    21436.18    22111.77
experime |  17,281    21874.26    173.9171    22862.65    21533.37    22215.16
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -100.2876    244.8394               -580.1808    379.6056
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    diff = mean(control) - mean(experime)                         t =  -0.4096
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3410         Pr(|T| > |t|) = 0.6821          Pr(T > t) = 0.6590
