
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     22000.6    174.6519    22959.25    21658.27    22342.94
experime |  17,281    21647.64    171.5801    22555.45    21311.33    21983.96
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            352.9601    244.8326               -126.9199    832.8401
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   1.4416
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9253         Pr(|T| > |t|) = 0.1494          Pr(T > t) = 0.0747
