
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21627.53    171.3015    22518.81    21291.76     21963.3
experime |  17,281    22020.71    174.9227    22994.86    21677.84    22363.58
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -393.179    244.8309               -873.0555    86.69753
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    diff = mean(control) - mean(experime)                         t =  -1.6059
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0542         Pr(|T| > |t|) = 0.1083          Pr(T > t) = 0.9458
