
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21680.72    172.1071    22624.72    21343.37    22018.07
experime |  17,281    21967.52    174.1361    22891.45     21626.2    22308.85
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -286.805    244.8351               -766.6899    193.0799
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    diff = mean(control) - mean(experime)                         t =  -1.1714
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1207         Pr(|T| > |t|) = 0.2414          Pr(T > t) = 0.8793
