
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21678.73    171.8734    22593.99    21341.84    22015.62
experime |  17,281    21969.51    174.3666    22921.75    21627.74    22311.29
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -290.7856     244.835               -770.6702     189.099
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    diff = mean(control) - mean(experime)                         t =  -1.1877
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1175         Pr(|T| > |t|) = 0.2350          Pr(T > t) = 0.8825
