
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21875.85    174.1222    22889.63    21534.55    22217.15
experime |  17,281    21772.39    172.1272    22627.36    21435.01    22109.78
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            103.4585    244.8394               -376.4347    583.3516
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    diff = mean(control) - mean(experime)                         t =   0.4226
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6637         Pr(|T| > |t|) = 0.6726          Pr(T > t) = 0.3363
