
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21825.81    174.2016    22900.06    21484.36    22167.27
experime |  17,281    21822.43    172.0477    22616.92     21485.2    22159.66
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            3.384769      244.84               -476.5096    483.2792
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    diff = mean(control) - mean(experime)                         t =   0.0138
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5055         Pr(|T| > |t|) = 0.9890          Pr(T > t) = 0.4945
