
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21845.62     174.923    22994.89    21502.75    22188.48
experime |  17,281    21802.62    171.3141    22520.47    21466.83    22138.42
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            42.99281    244.8399               -436.9014     522.887
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    diff = mean(control) - mean(experime)                         t =   0.1756
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5697         Pr(|T| > |t|) = 0.8606          Pr(T > t) = 0.4303
