
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22122.32    178.0736    23409.06    21773.28    22471.36
experime |  17,281    21525.92    168.0064    22085.65    21196.61    21855.23
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             596.401     244.819                116.5478    1076.254
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    diff = mean(control) - mean(experime)                         t =   2.4361
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9926         Pr(|T| > |t|) = 0.0149          Pr(T > t) = 0.0074
