
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21821.86    173.0842    22753.17     21482.6    22161.12
experime |  17,281    21826.38    173.1718    22764.69    21486.95    22165.82
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -4.521278      244.84               -484.4157    475.3731
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    diff = mean(control) - mean(experime)                         t =  -0.0185
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4926         Pr(|T| > |t|) = 0.9853          Pr(T > t) = 0.5074
