
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21605.58    171.9832    22608.43    21268.47    21942.68
experime |  17,281    22042.66    174.2495    22906.36    21701.12    22384.21
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -437.087    244.8287               -916.9593    42.78524
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    diff = mean(control) - mean(experime)                         t =  -1.7853
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0371         Pr(|T| > |t|) = 0.0742          Pr(T > t) = 0.9629
