
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21631.36    170.1433    22366.57    21297.86    21964.85
experime |  17,281    22016.89    176.0499    23143.03    21671.81    22361.96
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -385.5314    244.8312               -865.4086     94.3458
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =  -1.5747
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0577         Pr(|T| > |t|) = 0.1153          Pr(T > t) = 0.9423
