
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21880.92    173.8809     22857.9    21540.09    22221.74
experime |  17,281    21767.32    172.3708    22659.38    21429.46    22105.19
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            113.5925    244.8392               -366.3004    593.4854
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   0.4639
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6787         Pr(|T| > |t|) = 0.6427          Pr(T > t) = 0.3213
