
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21834.22    173.7676    22843.01    21493.62    22174.83
experime |  17,281    21814.02     172.486    22674.54    21475.93    22152.11
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            20.20646      244.84               -459.6879    500.1008
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    diff = mean(control) - mean(experime)                         t =   0.0825
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5329         Pr(|T| > |t|) = 0.9342          Pr(T > t) = 0.4671
