
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21899.94    174.2495    22906.35     21558.4    22241.49
experime |  17,281     21748.3    171.9973    22610.29    21411.17    22085.43
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            151.6447    244.8386                -328.247    631.5364
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    diff = mean(control) - mean(experime)                         t =   0.6194
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7322         Pr(|T| > |t|) = 0.5357          Pr(T > t) = 0.2678
