
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21981.51     174.582    22950.06    21639.31    22323.71
experime |  17,281    21666.73    171.6534    22565.08    21330.27    22003.19
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            314.7779    244.8341                -165.105    794.6608
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    diff = mean(control) - mean(experime)                         t =   1.2857
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9007         Pr(|T| > |t|) = 0.1986          Pr(T > t) = 0.0993
