
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21888.22    173.6281    22824.66    21547.89    22228.55
experime |  17,281    21760.02    172.6252    22692.82    21421.66    22098.39
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            128.1922     244.839               -351.7002    608.0847
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    diff = mean(control) - mean(experime)                         t =   0.5236
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6997         Pr(|T| > |t|) = 0.6006          Pr(T > t) = 0.3003
