
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21980.57    174.3203    22915.66    21638.89    22322.26
experime |  17,281    21667.67    171.9193    22600.03    21330.69    22004.65
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            312.9061    244.8342                -166.977    792.7891
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    diff = mean(control) - mean(experime)                         t =   1.2780
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8994         Pr(|T| > |t|) = 0.2012          Pr(T > t) = 0.1 006
