
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21682.95     170.742    22445.26    21348.28    22017.62
experime |  17,281    21965.29    175.4751    23067.47    21621.34    22309.24
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -282.336    244.8353               -762.2211    197.5492
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    diff = mean(control) - mean(experime)                         t =  -1.1532
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1244         Pr(|T| > |t|) = 0.2488          Pr(T > t) = 0.8756
