
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21905.52    173.3284    22785.27    21565.78    22245.26
experime |  17,281    21742.72    172.9252    22732.27    21403.77    22081.67
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            162.8027    244.8384               -317.0886    642.6941
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    diff = mean(control) - mean(experime)                         t =   0.6649
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7470         Pr(|T| > |t|) = 0.5061          Pr(T > t) = 0.2530
