
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21927.4    176.6172     23217.6    21581.21    22273.58
experime |  17,281    21720.85    169.5634    22290.34    21388.48    22053.21
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            206.5492    244.8375               -273.3403    686.4386
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   0.8436
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8006         Pr(|T| > |t|) = 0.3989          Pr(T > t) = 0.1994
