
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21632.29    171.8646    22592.84    21295.41    21969.16
experime |  17,281    22015.96    174.3701    22922.21    21674.17    22357.74
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -383.6713    244.8313               -863.5486    96.20608
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    diff = mean(control) - mean(experime)                         t =  -1.5671
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0586         Pr(|T| > |t|) = 0.1171          Pr(T > t) = 0.9414
