
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21952.38    174.0102     22874.9     21611.3    22293.46
experime |  17,281    21695.86    172.2358    22641.64    21358.26    22033.46
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            256.5208    244.8361               -223.3659    736.4076
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    diff = mean(control) - mean(experime)                         t =   1.0477
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8526         Pr(|T| > |t|) = 0.2948          Pr(T > t) = 0.1474
