
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21920.12    174.4917     22938.2     21578.1    22262.14
experime |  17,281    21728.12    171.7504    22577.83    21391.47    22064.77
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            191.9965    244.8378               -287.8936    671.8867
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    diff = mean(control) - mean(experime)                         t =   0.7842
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7835         Pr(|T| > |t|) = 0.4329          Pr(T > t) = 0.2165
