
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21668.71    171.6286    22561.82    21332.31    22005.12
experime |  17,281    21979.53    174.6065    22953.29    21637.28    22321.77
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -310.8122    244.8343               -790.6954     169.071
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    diff = mean(control) - mean(experime)                         t =  -1.2695
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1021         Pr(|T| > |t|) = 0.2043          Pr(T > t) = 0.8979
