
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21637.89    172.4548    22670.43    21299.87    21975.92
experime |  17,281    22010.35    173.7871    22845.57    21669.71    22350.99
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -372.4525    244.8318               -852.3309    107.4258
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    diff = mean(control) - mean(experime)                         t =  -1.5213
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0641         Pr(|T| > |t|) = 0.1282          Pr(T > t) = 0.9359
