
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22014.91    174.8459    22984.75     21672.2    22357.63
experime |  17,281    21633.33    171.3807    22529.22    21297.41    21969.25
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            381.5816    244.8314               -98.29589    861.4592
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    diff = mean(control) - mean(experime)                         t =   1.5585
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9404         Pr(|T| > |t|) = 0.1191          Pr(T > t) = 0.0596
