
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21959.33    175.0223    23007.94    21616.27    22302.39
experime |  17,281    21688.91    171.2066    22506.35    21353.33    22024.49
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            270.4195    244.8357               -209.4664    750.3054
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    diff = mean(control) - mean(experime)                         t =   1.1045
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8653         Pr(|T| > |t|) = 0.2694          Pr(T > t) = 0.1347
