
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22071.46    174.8747    22988.54    21728.68    22414.23
experime |  17,281    21576.79    171.3429    22524.26    21240.94    21912.64
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            494.6703    244.8255                14.80419    974.5363
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    diff = mean(control) - mean(experime)                         t =   2.0205
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9783         Pr(|T| > |t|) = 0.0433          Pr(T > t) = 0.0217
