
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21969.58    174.9464    22997.97    21626.67     22312.5
experime |  17,281    21678.66    171.2832    22516.41    21342.93    22014.39
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            290.9263     244.835               -188.9583    770.8109
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    diff = mean(control) - mean(experime)                         t =   1.1883
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8826         Pr(|T| > |t|) = 0.2347          Pr(T > t) = 0.1174
