
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21943.45    174.1258    22890.09    21602.14    22284.75
experime |  17,281    21704.79    172.1197    22626.38    21367.42    22042.17
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            238.6531    244.8366               -241.2347    718.5409
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    diff = mean(control) - mean(experime)                         t =   0.9747
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8352         Pr(|T| > |t|) = 0.3297          Pr(T > t) = 0.1648
