
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21972.73     174.881    22989.37    21629.94    22315.51
experime |  17,281    21675.52    171.3497    22525.15    21339.65    22011.38
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            297.2096    244.8348               -182.6746    777.0937
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    diff = mean(control) - mean(experime)                         t =   1.2139
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8876         Pr(|T| > |t|) = 0.2248          Pr(T > t) = 0.1124
