
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21945.17    175.8551    23117.42    21600.48    22289.87
experime |  17,281    21703.07    170.3523    22394.04    21369.16    22036.98
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             242.101    244.8365               -237.7866    721.9886
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   0.9888
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8386         Pr(|T| > |t|) = 0.3228          Pr(T > t) = 0.1614
