
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21804.54    171.4896    22543.54     21468.4    22140.68
experime |  17,281     21843.7     174.751    22972.28    21501.17    22186.23
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -39.15984    244.8399               -519.0541    440.7344
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    diff = mean(control) - mean(experime)                         t =  -0.1599
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4365         Pr(|T| > |t|) = 0.8729          Pr(T > t) = 0.5635
