
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21653.86    170.6644    22435.07    21319.34    21988.38
experime |  17,281    21994.38    175.5475    23076.99    21650.29    22338.47
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -340.5229    244.8332               -820.4039     139.358
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    diff = mean(control) - mean(experime)                         t =  -1.3908
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0821         Pr(|T| > |t|) = 0.1643          Pr(T > t) = 0.9 179
