
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21964.71    174.3509    22919.68    21622.96    22306.46
experime |  17,281    21683.53    171.8898    22596.16    21346.61    22020.45
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            281.1785    244.8353               -198.7067    761.0637
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    diff = mean(control) - mean(experime)                         t =   1.1484
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8746         Pr(|T| > |t|) = 0.2508          Pr(T > t) = 0.1254
