
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     22040.5    174.0687    22882.59    21699.31    22381.69
experime |  17,281    21607.74    172.1665    22632.52    21270.28    21945.21
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            432.7558    244.8289               -47.11694    912.6285
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    diff = mean(control) - mean(experime)                         t =   1.7676
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9614         Pr(|T| > |t|) = 0.0771          Pr(T > t) = 0.0386
