
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22025.17    174.2848    22910.99    21683.55    22366.78
experime |  17,281    21623.07    171.9499    22604.05    21286.03    21960.11
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             402.096    244.8305               -77.77966    881.9717
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    diff = mean(control) - mean(experime)                         t =   1.6423
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9497         Pr(|T| > |t|) = 0.1005          Pr(T > t) = 0.0503
