
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21974.25     177.343    23313.01    21626.64    22321.86
experime |  17,281    21673.99    168.8002       22190    21343.13    22004.86
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            300.2594    244.8347               -179.6245    780.1434
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =   1.2264
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8900         Pr(|T| > |t|) = 0.2201          Pr(T > t) = 0.1100
