
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21865.64    172.3867    22661.48    21527.74    22203.53
experime |  17,281     21782.6    173.8656    22855.88    21441.81     22123.4
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             83.0337    244.8396               -396.8599    562.9273
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   0.3391
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6327         Pr(|T| > |t|) = 0.7345          Pr(T > t) = 0.3673
