
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21802.53    173.4853    22805.89    21462.48    22142.58
experime |  17,281    21845.71    172.7699    22711.85    21507.07    22184.36
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -43.18763    244.8399               -523.0818    436.7066
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =  -0.1764
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4300         Pr(|T| > |t|) = 0.8600          Pr(T > t) = 0.5700
