
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21934.45    175.4565    23065.02    21590.54    22278.37
experime |  17,281    21713.79    170.7637    22448.12    21379.07     22048.5
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            220.6668    244.8371               -259.2219    700.5556
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   0.9013
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8163         Pr(|T| > |t|) = 0.3674          Pr(T > t) = 0.1837
