
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21805.78    172.2189    22639.41    21468.21    22143.34
experime |  17,281    21842.46    174.0323    22877.81    21501.34    22183.58
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -36.68596    244.8399               -516.5802    443.2083
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    diff = mean(control) - mean(experime)                         t =  -0.1498
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4404         Pr(|T| > |t|) = 0.8809          Pr(T > t) =  0.5596
