
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22023.63    174.7608    22973.57    21681.08    22366.18
experime |  17,281    21624.61    171.4663    22540.48    21288.52     21960.7
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            399.0163    244.8306               -80.85963    878.8923
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    diff = mean(control) - mean(experime)                         t =   1.6298
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9484         Pr(|T| > |t|) = 0.1032          Pr(T > t) = 0.0516
