
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21793.1    173.2736    22778.07    21453.46    22132.73
experime |  17,281    21855.14     172.982    22739.73    21516.08    22194.21
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -62.04496    244.8398               -541.9389     417.849
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    diff = mean(control) - mean(experime)                         t =  -0.2534
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4000         Pr(|T| > |t|) = 0.8000          Pr(T > t) = 0.6000
