
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21833.27    172.6775     22699.7     21494.8    22171.73
experime |  17,281    21814.98    173.5774       22818    21474.75    22155.21
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            18.28965      244.84               -461.6047     498.184
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   0.0747
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5298         Pr(|T| > |t|) = 0.9405          Pr(T > t) = 0.4702
