
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21952.25    176.0394    23141.66     21607.2    22297.31
experime |  17,281    21695.99    170.1612    22368.92    21362.46    22029.52
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            256.2603    244.8361               -223.6265    736.1471
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    diff = mean(control) - mean(experime)                         t =   1.0467
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8524         Pr(|T| > |t|) = 0.2953          Pr(T > t) = 0.1476
