
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21946.84    174.9672    23000.71    21603.89     22289.8
experime |  17,281     21701.4     171.264    22513.89     21365.7    22037.09
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            245.4453    244.8364               -234.4421    725.3328
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   1.0025
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8419         Pr(|T| > |t|) = 0.3161          Pr(T > t) = 0.1581
