
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21652.28    171.3472    22524.83    21316.42    21988.13
experime |  17,281    21995.96    174.8809    22989.36    21653.18    22338.75
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -343.688     244.833               -823.5687    136.1927
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    diff = mean(control) - mean(experime)                         t =  -1.4038
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0802         Pr(|T| > |t|) = 0.1604          Pr(T > t) = 0.9198
