
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21633.15    171.6394    22563.24    21296.72    21969.58
experime |  17,281    22015.09    174.5918    22951.36    21672.88    22357.31
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -381.9449    244.8314               -861.8224    97.93259
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    diff = mean(control) - mean(experime)                         t =  -1.5600
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0594         Pr(|T| > |t|) = 0.1188          Pr(T > t) = 0.9 406
