
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21945.46    174.9432    22997.55    21602.55    22288.37
experime |  17,281    21702.78    171.2886    22517.12    21367.04    22038.53
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            242.6774    244.8365               -237.2102     722.565
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    diff = mean(control) - mean(experime)                         t =   0.9912
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8392         Pr(|T| > |t|) = 0.3216          Pr(T > t) = 0.1608
