
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22029.93    174.2851    22911.03    21688.31    22371.55
experime |  17,281    21618.31    171.9489    22603.93    21281.27    21955.35
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            411.6208      244.83                 -68.254    891.4955
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    diff = mean(control) - mean(experime)                         t =   1.6813
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9536         Pr(|T| > |t|) = 0.0927          Pr(T > t) = 0.0464
