
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21876.01    173.2304    22772.38    21536.46    22215.56
experime |  17,281    21772.23    173.0247    22745.35    21433.08    22111.37
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             103.786    244.8394               -376.1072    583.6791
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    diff = mean(control) - mean(experime)                         t =   0.4239
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6642         Pr(|T| > |t|) = 0.6716          Pr(T > t) = 0.3358
