
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21877.11    172.5944    22688.78    21538.81    22215.41
experime |  17,281    21771.13     173.659    22828.73    21430.74    22111.52
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             105.982    244.8393               -373.9111    585.8751
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    diff = mean(control) - mean(experime)                         t =   0.4329
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6674         Pr(|T| > |t|) = 0.6651          Pr(T > t) = 0.3326
