
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21683.61     168.982     22213.9    21352.39    22014.83
experime |  17,281    21964.63    177.1706    23290.36    21617.36     22311.9
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -281.0183    244.8353               -760.9035     198.867
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    diff = mean(control) - mean(experime)                         t =  -1.1478
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1255         Pr(|T| > |t|) = 0.2511          Pr(T > t) = 0.8745
