
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21770.75    171.8362     22589.1    21433.93    22107.57
experime |  17,281    21877.49    174.4094    22927.37    21535.63    22219.35
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -106.7431    244.8393               -586.6362      373.15
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    diff = mean(control) - mean(experime)                         t =  -0.4360
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3314         Pr(|T| > |t|) = 0.6629          Pr(T > t) = 0.6686
