
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21950.67    173.1373    22760.15     21611.3    22290.03
experime |  17,281    21697.57    173.1134    22757.01    21358.25    22036.89
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            253.0924    244.8362               -226.7946    732.9794
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   1.0337
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8494         Pr(|T| > |t|) = 0.3013          Pr(T > t) = 0.1506
