
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21709.96    170.8739    22462.61    21375.03    22044.89
experime |  17,281    21938.29    175.3489    23050.88    21594.58    22281.99
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -228.3292    244.8369               -708.2176    251.5592
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    diff = mean(control) - mean(experime)                         t =  -0.9326
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1755         Pr(|T| > |t|) = 0.3510          Pr(T > t) = 0.8245
