
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21692.25    171.2693    22514.58    21356.55    22027.96
experime |  17,281    21955.99    174.9613    22999.92    21613.05    22298.93
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -263.7379    244.8359               -743.6242    216.1485
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    diff = mean(control) - mean(experime)                         t =  -1.0772
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1407         Pr(|T| > |t|) = 0.2814          Pr(T > t) = 0.8593
